Chromis died in QT

[boxed_reef]

I just lost 1 of 5 chromis that have been in 20 gallon QT for 25 days. Treated with 2 rounds of prazipro, along with feeding metro, and 2 weeks of coppersafe(approx 1.75ppm).
All remaining are still doing great, but the 1 that died stopped eating yesterday. It was one of the smaller ones, and he may have just gotten bullied. But he had some darker scales on his head, and I want to confirm it’s not uronema or something else I need to treat.
Don’t know if I should extend QT, or move them to the display to diffuse aggression. Any help is appreciated!

 

[Humblefish]

Although I don't see clear evidence of it here, Uronema is rampant amongst chromis damsels: https://www.reef2reef.com/threads/uronema-marinum.247940/