Massive graphical artifacts while using two displays and setting one to 4k resolution (Mavericks)

Hi everyone,

Recently I upgraded and got an Asus VP28U monitor. I want to use it together with my old Acer screen. I'm using HDMI for the old Acer monitor and DisplayPort for the new one. Everything is working alright, I have two separate displays but the Asus has to run in 2560x1440, otherwise, it massively glitches out and becomes totally unusable. I use clover as I also have a Windows boot on the same machine, 0 issues on Windows, both monitors running at their max resolution. I played around with installing Nvidia web drivers, os x default drivers and all the different injectors from Clover boot. I also tried changing from DisplayPort 1.2 to 1.1 and it still does not solve the issue. Here is a picture of what it looks like: https://imgur.com/a/xeIktKs

I'm still running Mavericks and my graphics card is GeForce GTX 660. Does anyone have a clue what may be causing the problem? Thanks!