PLZ Help with Sapphire 280X Dual x

[nskendrovic]

Hi all.
Im a beginer and i have 2 questions.
I have 1 Mbo with 2 gpus and 1 850w PSU.
I wana add 2 more gpu's...is it posible to just add another psu and conect it ionly to those 2 new gpu's or i have to upgrade to new biger psu and if so..would seasonic 1250 be enough?

Alos...as i mentioned i have 2 gpu's at the moment...1 is runing on 70C an other one on 90C..sometimes it gose til 94C...is that a problem or should i try undervolt them?

Ty in advance