Server crashes look the same

We currently have 3 servers, which all crash in sort of the same way.

First there is a huge lagspike, and then it crashes out of nowhere and leaves a Thread Dump in the console.

I've tried to find solutions to the problems the Thread Dump is giving, but can't seem to find any.

Here are the Thread Dumps of our 3 servers:

Survival: http://pastebin.com/eFy6tqHR
Creative: http://pastebin.com/Cmd1E2tz

Hub: http://pastebin.com/xLG0udmR

 

We started getting these a couple of days ago.

Please help us!

 

Thanks in advance!