I have a substantial gaming PC and it's always been able to run medium-large modpacks with very occasional stutters if any. Lately, however, it's been having trouble. Minecraft: Bedrock Edition and Minecraft: Java Edition (vanilla) both run great with no problems, but for some reason, my computer is hating modpacks. I run them and get 10-20 FPS with frequent FPS drops. I've tried modpacks with 60 mods up to 160, it just doesn't like them. I have also tried them with and without Optifine.
Weirdly, while it's running, Task Manager says my GPU is only being utilized 7%, could that be the problem? Please give me any ideas you've got and feel free to ask for more info.