Lagging and stuttering game performance when using screens in-game

Bluebellflora​ 

I actually had decent frame rate on the lot before the stutters and the FPS drops started. For comparison, here's a screenshot at 9:55am in game time, you can see sims using the computer without the FPS being affected (it's at 50fps which is fine for a community lot). This is why I said the issue doesn't seem related to screens in my case.

But after a while, the FPS drops and the stutters start (as seen in the screenshot I posted in my previous post, 11:11am in game time).