I would definitely try to determine if it's Ich or Velvet first.
I don't have any experience with velvet, but if it's ich...
--> I would remove the clown and start the tank transfer method (TTM) instead of copper. There's lot of information out there on this, and in my opinion, it's the least stressful on the fish. I do it with every new fish; it ensures that ich never gets into your display tank.
You also need to leave your display tank fallow (fishless) for at least 72 days to be sure ich is no longer present. The TTM takes about two weeks, and after that you'll have to have a quarantine tank for him to live in until the 72 days is up. I went through this exact process, and all the fish survived. If you get through it - and do TTM with every new fish - no more ich - ever!