Ive got two tangs in my 40b quarantine - They are on day 14 of QT, at 2.5 PPM of copper power. Yet, today, my purple tang broke out with dozens of ich spots. I have been dosing metro every 2 days with the copper power. Confused here as to how this can occur, when the water is at therapeutic levels. Any advice on where to go next? Tangs were just about to go into the main display (I knew they had ICH from a prior tank).