Hi all, last week we noticed signs of ich/ velvet on our mimic tang. He was scratching up against rocks .Unfortunately, that fish recently passed. The tank currently has a clown, 1 purple dottyback, and a pajama cardinal. The clown had ich around 7 years ago when we first set up the tank but since recovered. Currently, the cardinal and the clown look great with no signs of distress, eating, swimming, no white specks. The dottyback also is acting normally but has some visible white coating. I would expect the clown and cardinal to have it at this point but they don’t. My plan of action is to set up a 20 gallon QT and dose copper. Anything else I should be doing? Also, with the DT being fallow, how should I be giving that tank nutrients to keep my coral alive?