I would forget about the copper in the QT. Do a water change and cleanup the QT to prepare for new fish. Also, when you QT fish, it should be 1 at a time, unless you have a sizable QT.
If you new fish have ich, then you will need to either do hyposalinity [preferable] or go back to copper. Copper does no good unless it is maintained at theraputic levels. Copper is not healthy for fish.