Built a new rig and my hashrate is down...

Old rig:
MB: ASROCK H81 Pro BTC 2.0
CPU: Intel Pentium G3260 (3.3GHz)
RAM: 8GB - 1333MHz
6GPU

New rig:
MB: Asus B250 Mining Expert
CPU: Intel Celeron G3930 (2,9Ghz)
RAM: 8GB - 2400MHz
updated Bios + Chipset to latest version
9GPU

Dual mining ETH+XVG with Claymore 11.7
Both times Radeon drivers 18.3.1, all compute.
4 of my cards that used to mine ETH at 30Mh/s and now do only 28,3 in my new rig... Those cards are on the same PSU I used in the old rig.

OC/UV used to be 1130 / 2035 / 890 / 890
Tried pushing them to 1130 / 2100 / 880 / 880, but I get minimal gain and seem to have touched the ceiling as I start getting invalid shares and have to get back to safer levels.

This might seem silly, but is it possible I have to flash the BIOS of the GPUs again as the configuration is different? Latest Windows10, so problems with ATIFlash to check... :-(

Thanks for any help