Factions and other plugin issues

I have been working on a server for about a week now. And I did recently release it, but I am still setting up more aspects of it. Mostly because of some of the issues in loading plugins.

Can someone please explain how these problems are cause and how to fix them

Code:

[14:47:21] [Server thread/ERROR]: Could not load 'plugins/mcore.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: com/massivecraft/mcore/MCore : Unsupported major.minor version 51.0
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:328) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.loadPlugins(CraftServer.java:355) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.<init>(CraftServer.java:317) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PlayerList.<init>(PlayerList.java:68) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedPlayerList.<init>(SourceFile:14) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedServer.init(DedicatedServer.java:126) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java:436) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:628) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
Caused by: java.lang.UnsupportedClassVersionError: com/massivecraft/mcore/MCore : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.6.0_32]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:643) ~[?:1.6.0_32]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.6.0_32]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:277) ~[?:1.6.0_32]
    at java.net.URLClassLoader.access$000(URLClassLoader.java:73) ~[?:1.6.0_32]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:212) ~[?:1.6.0_32]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.6.0_32]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205) ~[?:1.6.0_32]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:77) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:323) ~[?:1.6.0_32]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:268) ~[?:1.6.0_32]
    at java.lang.Class.forName0(Native Method) ~[?:1.6.0_32]
    at java.lang.Class.forName(Class.java:270) ~[?:1.6.0_32]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:127) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    ... 9 more
[14:47:21] [Server thread/ERROR]: Could not load 'plugins/AntiXRay.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: me/ryanhamshire/AntiXRay/AntiXRay : Unsupported major.minor version 51.0
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:328) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.loadPlugins(CraftServer.java:355) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.<init>(CraftServer.java:317) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PlayerList.<init>(PlayerList.java:68) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedPlayerList.<init>(SourceFile:14) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedServer.init(DedicatedServer.java:126) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java:436) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:628) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
Caused by: java.lang.UnsupportedClassVersionError: me/ryanhamshire/AntiXRay/AntiXRay : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.6.0_32]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:643) ~[?:1.6.0_32]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.6.0_32]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:277) ~[?:1.6.0_32]
    at java.net.URLClassLoader.access$000(URLClassLoader.java:73) ~[?:1.6.0_32]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:212) ~[?:1.6.0_32]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.6.0_32]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205) ~[?:1.6.0_32]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:77) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:323) ~[?:1.6.0_32]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:268) ~[?:1.6.0_32]
    at java.lang.Class.forName0(Native Method) ~[?:1.6.0_32]
    at java.lang.Class.forName(Class.java:270) ~[?:1.6.0_32]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:127) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    ... 9 more
[14:47:21] [Server thread/ERROR]: Could not load 'plugins/killstreak.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: me/jonneystechcheck/kill/streak/Killstreaks : Unsupported major.minor version 51.0
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:328) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.loadPlugins(CraftServer.java:355) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.<init>(CraftServer.java:317) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PlayerList.<init>(PlayerList.java:68) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedPlayerList.<init>(SourceFile:14) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedServer.init(DedicatedServer.java:126) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java:436) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:628) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
Caused by: java.lang.UnsupportedClassVersionError: me/jonneystechcheck/kill/streak/Killstreaks : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.6.0_32]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:643) ~[?:1.6.0_32]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.6.0_32]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:277) ~[?:1.6.0_32]
    at java.net.URLClassLoader.access$000(URLClassLoader.java:73) ~[?:1.6.0_32]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:212) ~[?:1.6.0_32]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.6.0_32]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205) ~[?:1.6.0_32]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:77) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:323) ~[?:1.6.0_32]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:268) ~[?:1.6.0_32]
    at java.lang.Class.forName0(Native Method) ~[?:1.6.0_32]
    at java.lang.Class.forName(Class.java:270) ~[?:1.6.0_32]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:127) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    ... 9 more
[14:47:21] [Server thread/ERROR]: Could not load 'plugins/DeathMessages.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: com/gmail/josemanuelgassin/DeathMessages/_DeathMessages : Unsupported major.minor version 51.0
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:328) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:251) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.loadPlugins(CraftServer.java:355) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.<init>(CraftServer.java:317) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PlayerList.<init>(PlayerList.java:68) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedPlayerList.<init>(SourceFile:14) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedServer.init(DedicatedServer.java:126) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java:436) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:628) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
Caused by: java.lang.UnsupportedClassVersionError: com/gmail/josemanuelgassin/DeathMessages/_DeathMessages : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.6.0_32]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:643) ~[?:1.6.0_32]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.6.0_32]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:277) ~[?:1.6.0_32]
    at java.net.URLClassLoader.access$000(URLClassLoader.java:73) ~[?:1.6.0_32]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:212) ~[?:1.6.0_32]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.6.0_32]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205) ~[?:1.6.0_32]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:77) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:62) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:323) ~[?:1.6.0_32]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:268) ~[?:1.6.0_32]
    at java.lang.Class.forName0(Native Method) ~[?:1.6.0_32]
    at java.lang.Class.forName(Class.java:270) ~[?:1.6.0_32]
    at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:40) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:127) ~[craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    ... 9 more
[14:47:22] [Server thread/ERROR]: Could not load 'plugins/Factions.jar' in folder 'plugins'
org.bukkit.plugin.UnknownDependencyException: mcore
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:216) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.loadPlugins(CraftServer.java:355) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.<init>(CraftServer.java:317) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PlayerList.<init>(PlayerList.java:68) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedPlayerList.<init>(SourceFile:14) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedServer.init(DedicatedServer.java:126) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java:436) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:628) [craftbukkit-beta.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]

Help is much appreciated.

 

is the mcore the right version?

 

There was something wrong with the Factions I update to Factions for 1.8 servers and it works fine on my 1.7.9 server