Clown goby death during copper treatment

[Breadbox]

Unfortunately both of my ich-ridden green clown gobies did not survive the copper treatment in QT, they aren't eating well and hadn't eaten for a few days so I know it's a big factor.

But I have also noticed that they are losing colors and fins before and when they died, they basically have no colors and fins left when they died, I'm wondering if this is a sign of something else at play. Since my royal gramma is also losing colors (tho its energy and appetite has improved after a few days in copper), I'm wondering if it's something else i should be worried about for my other fishes in QT.

Sorry there's no photo, but the symptoms are exactly as described, completely pale before and after death, missing fins. Also, is it possible that the copper in the water killed the clown gobies?

 

[Tamberav]

likely related to ich or secondary infection. It would not make sense for copper to erode their fins.