Perhaps one of the mods get updated while the other didn't and now they're interfering with eachother. If the mods are not completely necessary I would get rid of them or atleast try reinstalling them.
Nope, I was getting perfectly fine FPS with the mods the day before. And the mods don't have an auto-update system or anything.
I tried without the mods, still got horrible FPS. I also completely re-installed the game and I'm still getting horrible FPS.