Is this normal (fluctuation)

Hi guys, i have a problem and i want to know if someone can help me.
As you can see in the pic, my hash rate fluctuates between 35 and 70 while my reported hashrate is 57.5.
Is this normal or my vga is thorthling?
Both (RX580 AND 480) are modded with 1500 timmings .
Temps seems normal (less than 70 degrees)
Clocks and voltage : 1150/1000 2000/960 both.
My psu : evga 850w gold


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Thanks in advance