Cpu&gpu lowers after a time

[emirsenkul]

I have my gpu usage %90-95 and cpu 60-80 having 170fps in rainbow:6 siege pretty good but when i close the game and surf in the internet for 3-4 hours when i go back to game gpu usage is 70ish and cpu is 15-20 i get 108 fps everytime but when i restart the pc it goes normal again i dont know what causes this it happens every game
By the way if i dont stop playing for like 12 hours or keep the game open it works perfectly but when i close the game and surf for a bit in youtube it starts having that problem
pc specs:
i7 8700k
1080ti
z370
2x8 3000mhz ram

 

[emirsenkul]

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