Memory maxed out on server

Running a snapshot server with roughly 5-12 players at once.

 

Regardless of how much memory is allocated to the server, I've tried 4GB, 6GB and 8GB so far, the server will end up max-ing out regardless of how many players are online.

Things start fine but eventually once there is around 10 people on usage will be high but 2 hours later when there is 1 person on the memory usage is still at 100%.

 

Constant restarts are the only thing that fix this.