There can be a lot of things to cause this problem. I'll give you some solutions, that I know that might work.
1) Go to FeralHeart > Media > Particles And search for any file there that ends with '_0' or other numbers. If there are those particles, DELETE THEM.
2) Delete any new meshes that you might have downloaded that are causing the problem.
3) Uninstall FeralHeart (also removing the FH folder.), then reinstalling it.
4) Also, it might be your computer. If it's old/slow, that might be the problem. You can update your driver or buy a new one.
I hope I helped somehow. Good luck!