Degraded shader performance over time?

Sorry if this is incoherent:

Whenever I open up my world, I can get maybe 2-3 minutes of good (enough) performance w/ shaders and DH on, but it quickly degrades and I have to look directly up at the sky to even just navigate menus, otherwise my entire computer freezes.

I can still walk and stuff, it's just that my GPU just... gives up, I guess.

This is a recent issue, and hadn't happened before even with the same exact shaders and DH installed. I used to get pretty good performance.

I've tried:

• Running only Oculus and the shaders I want, and they work fine. DH also works well. Adding mods seems to ruin it.
• Reducing shader quality settings

I allocated a ton of memory, and I have 8GB VRAM. (2080 and a 12700kf). I'm on Forge 1.20.1. I'm not sure how to share my modlist efficiently.

Any ideas as to what this could be caused by? Sorry if I've missed something stupid, if this is a common/stupid question, and if this is the wrong place to ask.