So my monitor setup is 1 Samsung t24c300 and a AOC 2460pf the t24 is connected to my gpu via a hdmi cable (A msi radeon rx 480 8gb) and the AOC monitor via a dp cable also to my gpu. It happenned after I connected the monitors to my GPU so it is a GPU problem.
I already tried changing the colordepth in CCC for the t24 it made it a bit worse but for the AOC monitor it changed nothing and I changed the pixel layout in CCC but that changed nothing. And I also tried reinstalling the drivers with DDU but that also did nothing. And connecting the monitors apart from each other also did nothing.
Here is a link to an album with pictures showing the problem (SFW): http://imgur.com/a/GgkdZ