How did you mod the bios do you change the values yourself on each card or just find a .rom on the internet for the same model/memory?
I wouldn't be dual mining sia at the moment either since the introduction of the Bitmain A3 just mine Ethereum
Download SMOS or Hive OS and try that instead of windows - see what sort of hashrate you are getting I would be looking at 28-30 as the average for an RX 580.
it wont let me send another personal msg for an hour.
when you say miner do you mean like the claymore miner