I have a couple of tangs in quarantine and tank is at 2.35 therapeutic Copper Power for the last 5 days and all was good until during feeding this morning I noticed some white stuff on one of my tangs pecks. Thinking it may have been flukes I did a 4 min fresh water dip and nothing fell off. He is eating well and no flashing or rubbing against the tank glass. Not sure what to do since he is in copper treatment. Need some assistance with identification and treatment.