The solution turned red and the gold dissolved after you switched to a steel anode. Could the culprit oxidizer here be ferric chloride? A steel anode in a hot HCl solution rapidly dissolves to vivid red ferric ions. This paper indicates ferric chloride can dissolve gold in a hot acidic solution:
https://acris.aalto.fi/ws/portalfil...netics_and_mechanisms_of_gold_dissolution.pdf
Generally I run electrowinning with a lab power supply in constant current mode so I get to decide the amperage--to get clean metal separation in a lab scale experiment, I've had better results from small currents well under one amp. At high amperage, the gas bubbles can rapidly change the pH (due to directly removing hydrogen as a gas!), as well as creating corrosive hazardous mists.
