sounds like a poor quality psu.

i do 750 on volt setting 6 not volt setting 7.

you are running 4 units on the psu.

so what is the make and model of the psu?

you would want a plat that can do  750-1000 watts and it has 1 rail.

I will link some for you.

https://www.evga.com/products/product.aspx?pn=210-PQ-0850-X1

10 year warranty should be quiet and is a plat  the 12 volt rail will do 840-850 watts 160 but  you spent 1200 on 4 units.