Ich will not make a fish not eat especially if you have the fish in copper. That is unless it’s ich infestation on the fish. Flukes will cause that and ammonia could also. Depending on your QT tank setup, how long you had the fish in QT and so on can effect the fishes eating. Pinched belly sounds like it’s been days without food.
Some things to keep in mind about QT. How the fish is swimming, breathing, eating, even reacting to light, wanting to hide or shy and entire time in QT, (this one can be fish based also), and these are things to keep in mind that even in a regular tank.
The naso I saw in the pic above could also be showing stress markers. Have seen this in them when in holding tanks, or QT. BUT can also be fluke cones, or ich cones. The cones are markers where a diseases emerges and drops off from on the body of the fish.
How did you setup your QT tank? Aeration in good amount? Dosing of bacteria? Keeping water clean?
As for the ammonia badge, just so you know, once you touch it it’s pretty much shot from what I know.