Hashrate Drop on 2 cards! Need Help!

Hi,

i have 4x PowerColor Red Devil 8GB. I tested with standard BIOS all fine!

I have flashed them to Anoraks LowPwr Custom BIOS.

But now the first and the third cards drops in hashrate??? (ETH Mining Claymore 7.4 or 8.1 the same)

Iam using Win10 x64, Asrock BTC 2.0 Board, 8GB RAM and PCIe Risers.

Drivers are 16.11.5 AMD for Win10.

16GB Virtual Memory is set.

Any ideas?