This is exactly what im currently going through. Ive tested this: fortnite runs 100+, minecraft 100+, cs 80+ on SOME maps, mw multiplayer 60ish. In menu in cs, 400+, in game 70ish and WILL dip to like 40. mw warzone 30>. All these games ran perfectly fine before. Idk why a $500 machine is doing this