Anyone having low FPS In certain game but in other games it was ok?

First day switch to window 10 , everything was fine until few days later things started to go wrong.

Game like Cs go I can achieve 100 FPS, shadow of mordow (average 80 FPS)

But game like Guild wars 2 all of sudden it drop to 10 FPS o.O , same happen to heroes of storm when in menu the FPS only stay at 10++ FPS?

Btw, all driver is latest, I have reinstall a clean window 10 Pro still no fix.

is resetting a PC and reformat using ISO the same thing? is it possible file corrupted in drive C so resetting the PC might not fix the problem instead install through ISO might be safer?

i am one of the user that got free 1 year upgrade from window 8.1, now i already activated the WIndows 10, so if i install a new windows 10 again using ISO. will my key usable? Advise?

Thanks.

ok thanks for the info but i think microsoft give me the Pro version. =)