Server is lagging [JB7]

I am running a JB7 Server and every few seconds there are lag spikes.

Further I have 3 TTT and 1 Deathrun Server on the same dedicated server. These servers are running fluently.

Server: i7-3770, 16GB RAM, 1GBit up/down

The CPU usage is between 20%-50%

I hope that you have some suggestions for me.

What addons are you running?

Not much.

(Red ones are coded by me, they should not be a problem)
I use all these addons also on my TTT/DR server and they are ok.

Make sure you are running your srcds instances on different threads/cores

Every Server now uses a different core and the server still laggs.