/opt/zextras/common/bin/java -Dfile.encoding .... TOO many Process and consumes memory in a day

I had a fresh install of carbonio. I am using it since 2 weeks. The server is actively used by 3 person and I allocated 16 GB RAM (I migrated data from Zimbra)

But almost everday the server responds slow and when I checked with htop the process described in the topic consumes memory and it keeps it.

What is the problem? https://imgur.com/a/YZ606LR