Hi again all,

Thanks for all the pointers, I have figured out what the issue is and it is indeed the motherboard.

Because it's a lower end board it seems that the PCI Lanes actually share bandwidth, so this was causing the 'slow down'.

I decided to check each GPU on their own in their current slots, and with the other GPU's removed they ran at full tilt.

So the issue will be fixed completely when my new board arrives.

Thanks again for the help.

TheMightySpud