I need assistance please. Marine velvet.

[Abe]

I have few fish in a quarantine tank. I found the last one I bought wich was on the weekend today with redish spots on it body and swiming on top of tank. I believe its marine velvet. As soon as I seen it I took it out and place it in a tot with powerhead and heater for now as I was on my way out to work. I am planing to start using copper on it and add a small filter and hopefully it will recover. My question is, what about the other fish I had with it. Are they safe?or should I use copper as well. The only thing is I have few frags in there as well as some CUC. Let me know what should I do. Thanks.