I'm using Gigabyte Aorus RX580's and just can't get past 831 H/s per card.

This is my first rig and the riser cards didn't turn up (thanks Amazon!!) so I can only run one card at a time at the moment plugged directly in to the mobo.  Can the hash rates increase once I have them attached via the riser cards?

I realise now these were not the best choice of RX580s out there but is anyone else with an Aorus seeing better results?