Excessive Server Memory usage ?

I run a 1.9 Snapshot server so went to 8GB for the server an found it was also using the entire 8GB of memory .. So ive now gone to a 16GB server dedicated box and its consuming all the 16GB .. which i find is complete and utterly rediculous ....

The server gets to the stage where Block lag is redicuously high and the rubberbanding effect takes place, both noticable in players an also when viewing the sky to the point the server isnt playable untill such time as a restart occurs or Watchdog forcibly crashes the server.

So i feel there is possibly some sort of a leak somewhere as a basic Vanilla server esp snapshot should not be consuming this much RAM ever.

My user count is avg 20-40 users, we dont use spreadplayers, Spawn protection is set @ 150, View Distance is set to 10

Ive done multiple world resets over the last few mnths testing usage of command blocks to not using them etc and not made a difference

The start command at its basic is..

command = "{JAVA}" -Xmx{MAX_MEMORY}M -Xms{START_MEMORY}M -Djline.terminal=jline.UnsupportedTerminal -jar "{JAR}" nogui