It looks like you have an Asrock board.
Which one is it?
It is recommed to use a special mining mainboard. Much less problems, and its cheap.
I have a ASrock H110 Pro BTC+
The thing is all my cards works perfectly when i run them solo.
I can also drive my gtx970 and my gtx1070 at the same time no problem, but when it comes to my 1050 it dosent work with the other cards. i think its something with the drivers that fucks everyhing up.
All the cards are working so it shouldnt be any problem and i have a Evga Supernova G2 1300W so 3 cards shouldnt be a problem.
i have been trying to fix this damn problem for lik 4 hours now.
my rigg spec to simplyfi
CPU: Celeron G3930
Motherboard: ASrock H110 Pro BTC+
PSU: Evga Supernova G2 1300W
Geforce GTX 970 4g
Evga Geforce GTX 1050 2g
MSI Geforce GTX 1070 8g