Crash Server uses 600% of the RAM and Crashes

One of my servers keep increasing CPU usage at some point (up to 600-700% of the CPU ! INSANE!) and then in console it tries to crash but can't even crash and I have to kill the process to stop it!

other servers are fine. only one server happens to do this and then cause lag on other servers too because it uses most of the CPU. here is the crash log:

Code (Text):

[09:17:30] [Spigot Watchdog Thread/ERROR]: The server has stopped responding!
[09:17:37] [Spigot Watchdog Thread/ERROR]: Please report this to http://www.spigotmc.org/
[09:17:37] [Spigot Watchdog Thread/ERROR]: Be sure to include ALL relevant console errors and Minecraft crash reports
[09:17:37] [Spigot Watchdog Thread/ERROR]: Spigot version: git-Spigot-870264a-0a645a2 (MC: 1.8.3)
[09:17:37] [Spigot Watchdog Thread/ERROR]: ------------------------------
[09:17:37] [Spigot Watchdog Thread/ERROR]: Server thread dump (Look for plugins here before reporting to Spigot!):
[09:17:44] [Spigot Watchdog Thread/ERROR]: ------------------------------
[09:17:44] [Spigot Watchdog Thread/ERROR]: Current Thread: Server thread
[09:17:48] [Spigot Watchdog Thread/ERROR]:     PID: 16 | Suspended: false | Native: false | State: RUNNABLE
[09:17:48] [Spigot Watchdog Thread/ERROR]:     Stack:
[09:17:48] [Spigot Watchdog Thread/ERROR]:         java.io.FileInputStream.<init>(FileInputStream.java:143)
[09:17:48] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.WorldNBTStorage.checkSession(WorldNBTStorage.java:68)
[09:17:48] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.World.checkSession(World.java:2833)
[09:17:58] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.ChunkRegionLoader.a(ChunkRegionLoader.java:134)
[09:18:01] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.ChunkProviderServer.saveChunk(ChunkProviderServer.java:251)
[09:18:01] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.ChunkProviderServer.unloadChunks(ChunkProviderServer.java:357)
[09:18:01] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.WorldServer.doTick(WorldServer.java:234)
[09:18:01] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.MinecraftServer.A(MinecraftServer.java:767)
[09:18:01] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.DedicatedServer.A(DedicatedServer.java:368)
[09:18:33] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.MinecraftServer.z(MinecraftServer.java:651)
[09:18:33] [Spigot Watchdog Thread/ERROR]:         net.minecraft.server.v1_8_R2.MinecraftServer.run(MinecraftServer.java:554)
[09:18:33] [Spigot Watchdog Thread/ERROR]:         java.lang.Thread.run(Thread.java:745)
[09:18:33] [Spigot Watchdog Thread/ERROR]: ------------------------------
[09:18:58] [Spigot Watchdog Thread/ERROR]: Entire Thread Dump:
[09:23:57] [Spigot Watchdog Thread/ERROR]: ------------------------------
[09:25:33] [Spigot Watchdog Thread/ERROR]: Current Thread: process reaper
[09:28:30] [Spigot Watchdog Thread/ERROR]:     PID: 3644 | Suspended: false | Native: false | State: RUNNABLE
[09:28:30] [Spigot Watchdog Thread/ERROR]:     Stack:
[09:28:30] [Spigot Watchdog Thread/ERROR]:         java.lang.UNIXProcess.waitForProcessExit(Native Method)
[09:28:30] [Spigot Watchdog Thread/ERROR]:         java.lang.UNIXProcess.access$500(UNIXProcess.java:54)
[09:28:30] [Spigot Watchdog Thread/ERROR]:         java.lang.UNIXProcess$4.run(UNIXProcess.java:227)
[09:28:30] [Spigot Watchdog Thread/ERROR]:         java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
[09:28:30] [Spigot Watchdog Thread/ERROR]:         java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
[09:28:30] [Spigot Watchdog Thread/ERROR]:         java.lang.Thread.run(Thread.java:745)
[09:28:30] [Spigot Watchdog Thread/ERROR]: ------------------------------
[09:28:35] [Spigot Watchdog Thread/ERROR]: Current Thread: ProtocolLib-StructureCompiler 0
[09:28:35] [Spigot Watchdog Thread/ERROR]:     PID: 343 | Suspended: false | Native: false | State: WAITING
[09:28:35] [Spigot Watchdog Thread/ERROR]:     Stack:
[09:28:35] [Spigot Watchdog Thread/ERROR]:         sun.misc.Unsafe.park(Native Method)
[09:28:35] [Spigot Watchdog Thread/ERROR]:         java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
[09:28:35] [Spigot Watchdog Thread/ERROR]:         java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
[09:28:35] [Spigot Watchdog Thread/ERROR]:         java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
[09:28:39] [Spigot Watchdog Thread/ERROR]:         java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068)
[09:28:39] [Spigot Watchdog Thread/ERROR]:         java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
[09:28:46] [Spigot Watchdog Thread/ERROR]:         java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
[09:28:49] [Spigot Watchdog Thread/ERROR]:         java.lang.Thread.run(Thread.java:745)
[09:29:24] [Spigot Watchdog Thread/ERROR]: ------------------------------
[09:29:24] [Spigot Watchdog Thread/ERROR]: Current Thread: pool-8-thread-5
[09:29:24] [Spigot Watchdog Thread/ERROR]:     PID: 134 | Suspended: false | Native: false | State: WAITING
[09:29:28] [Spigot Watchdog Thread/ERROR]:     Stack:
 

Edit: Thanks for all the help guys, but I find out what was the problem. It was because of the "WorldBorder" Plugin which I forgot to update it (still was version 1.7.9). so when players reach the edge of the world, the server would go insane and couldn't handle it for some reason.
Updated "WorldBorder" plugin to the latest version and now everything works fine. With more than 8 Servers setup, the total CPU usage is now under %5. which is quite fantastic!

 

running on :1.8.3.
And what I dont get is why it takes the CPU to the next level?! %600?!! REALLY (((((