Huge decrease in FPS (Use of abilitys)

Mainly happens when i use Yasuo, the FPS is around 20-24 normally which is a bit laggy, but when i get my whirlwind on his q, the FPS goes down to 10-12 Not seem like much but in teamfights (any champ) the fps goes down to 2-4 My graphic card is bad but is there any way i can tune down the settings ingame? Video quality is down to Very Low
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