FPS suddenly wont go above 34 max and below 25-15 on average. even around 5 a few times.

So Minecraft used to run on average without any mods installed at around 400 fps and had no issues. Recently the fps has been incapable of going above 30 and is overall just running very poorly. This has to be an issue with the game itself as i have no issues with any other games. I am aware That I only saw whatever my monitors refrsh rate is set to its just annoying that I suddenly have to play super choppy game when it ran perfectly before, and yes it does affect every version I checked. If you could provide me with an answer as to why this suddenly occured that'd be wonderful thank you. I have tried many methods o fix it on my own and they don't seem to work. It should still be running fine but isn't for some reason. To clarify this is on every update not just 1.16.4