FPS is Shot

So I started playing GTNH on curseforge: major sin, I know. After reading about all the nonsense with that particular mod loader and with the release of 2.8, I figured I should migrate over to prism. Downloaded everything off the official website, set up my instance, managed to copy my save over and everything. The only problem is my FPS is now absolutely nuked. I’m only at the start of the steam age so it’s not like I have a ton of machines running by any means. On curseforge I was getting an average of 60 fps with occasional drops as I generated new terrain or whatever, now I can’t seem to break 16. I already messed with the memory allocations and Java arguments too. Any ideas? Thanks!