I would want them eating with gusto, pretty much when they came out of the bag at home.
I certainly wouldn't sell clownfish at retail that were behaving like you're describing.
If you agree that the med's are an impediment to them eating, then however soon you are able to be done with the med treatments you should be done with them and get the clowns into normal, clean seawater. Even if it's still in the QT for more observation.
I don't know enough about what you're doing to say "rush it" but certainly do not add more time onto whatever treatments you're doing. Know what I mean?
Clowns are nasty little carnivores
with teeth....they ought to be acting like it by now. Yours are acting
weird. You ought to flinch when you put your hand in the tank cuz you think they're gonna bite you again. That should be your goal for them!

They should not be timid from a mysis shrimp...that's not a positive sign.