I can't help but to pay close attention to this thread. The end of last year I introduced flukes via snails, lost some fish, saved my Muelleri and clown pair. Later in qt the female clown attacked the male who died several days later from his injuries. I attempted to add a new male into the female's qt, he brought velvet into the mix, although he didn't show signs for 2-3 weeks and the female showed symptoms first. I used cholorquine for 10 days w/fw dips (fw dips are essential for velvet relief!) and I questioned the effectiveness of the cp, so I switched to copper and after a round of septicema (cured by feeding erythromycin in frozen food for a few days) the female, who I've had 10 years has been fully recovered and thriving for many months. The moral of my story is if you think it's velvet, look for a pinched appearance, a powdery sheen, and no skin peeling, then I would opt for Copper w/fw dips. It's quite possible that ich and velvet were introduced into your tank.