Just something I noticed:
Running a RX570 4GB in combo with 3 RX550 2GB results in ~10% less reported hash on the RX570
Default core voltages of 1150mV for at least the RX570 can be of an issue and give clearly lower hash rates (~20%, or no hash at all) compared to other settings with like 1000-950 mV
1150mV is very high, stock settings are often crazy compared to optimal settings. Sounds like youre being throttled, thermal or power limit, hence the worse performance.