My power supply is the corsair hx1000. Even 800W should be enough. And when I run the Heaven Benchmark, it stresses my cards at 100% with no issues, where FFXIV only pushes them to about 60% at 4k 60 for capped. Thank you for the advice though, I'll try testing it when I get a chance just to be sure.

One thing I'm going to try is replacing the DP cable. When I got the monitor a couple years ago I just picked one up not knowing that back then there were few VESA certified cables, and the one I purchased wasn't one. I've read that the uncertified cables can cause a bunch of random stuff to happen. I hope this is the case with me.