Try 1 card and add 1 by 1.
Try Mining after each step.
I had a defect GPU which showed up perfectly but crashed after 5% load.....sucked....
Might be a broken Riser or Molex.
I think (hope) you are talking about the B250 Mining Expert.
It should show running GPUs after Bios. If you didnt deactivate it.....
Dont put 1 GPU in the X16 Slot, all must be in X1.
Try simplemining, its a much faster test and free for a while.
I have 2070super Rigs and they run perfect.
But i avoid mixing GPUs.
Thanks.
All Risers are fine as I tested them on 2070 super alone, and all worked and have been mining for 4 days.
I installed 2080 super and only it was detected and 2070 super though Device manager shows it with Exclamation mark, None of the miner programs detect it.
I removed 2070 and installed I tried 1 by 1 both the 2080, both worked fine and mined. I added 2070 back but again it was not detected.
Tried DDU a couple of times but same issue.
I have 1200 Corsair PSU.
I have always installed the GPU connected to monitor in x16 slot. Will try in x1 and report back.