Finally got around to updating to new drivers today, and have been having major issues ever since. Any game I open starts out at 60+ fps like normal for just a few seconds, then immediately plummets to between 6 and 10fps. I traced the problem to some degree to the fact that I'm running an extended monitor display (main gaming one, old one for discord or youtube on the side). When I disconnect that monitor entirely, everything goes back to normal, but whenever it is connected my games all sit around 8fps. Tested most extensively on the Witcher III and Overwatch (made sure to try one from battlenet and one through steam). Have tried disabling FreeSync and also running fullscreen instead of in borderless windows, to no effect. I really don't want to have to unplug my second monitor during the time I use it the most, so any help would be much appreciated! Thank you!
Edit: Just to be crystal clear, this issue is only while in games as well, FPS is totally normal outside of that.
Other notes: When I fullscreen (drag to top) windows in my second monitor, the edge now bleeds over into my main one. I also get rainbow lines fizzing across my screen for short while after each startup. All of this is new behavior since I updated drivers.