what I would do is ditch the stress coat and zhyme (once you've used it up of course, no sense in wasting it) Both stress coat and stress zhyme contain aloe vera and there has been some research recently that shows that aloe vera affects fishes gills.
Now, I don't think for one minute that you've caused this, purely because the fish are new, I think this originated at the lfs and you just got unlucky. But I see no sense in potentially harming fish with aloe vera. I myself have used a dechlor containing aloe vera for years but once I heard about the potential harm caused by it I used up the dechlor I have and searched for one that doesn't contain it. I now use API Tap Water Conditioner. It's highly so concentrated and I only use 1ml to dechlorinate 60 litres! Another one that doesn't contain aloe vera is Seacham Prime but getting that here in the U.K difficult - certainly in my area anyway
Is your hospital tank cycled? I'm concerned he's now going to be exposed to ammonia and nitrite which in his weakened state will likely kill him in hours
Now, I don't think for one minute that you've caused this, purely because the fish are new, I think this originated at the lfs and you just got unlucky. But I see no sense in potentially harming fish with aloe vera. I myself have used a dechlor containing aloe vera for years but once I heard about the potential harm caused by it I used up the dechlor I have and searched for one that doesn't contain it. I now use API Tap Water Conditioner. It's highly so concentrated and I only use 1ml to dechlorinate 60 litres! Another one that doesn't contain aloe vera is Seacham Prime but getting that here in the U.K difficult - certainly in my area anyway
Is your hospital tank cycled? I'm concerned he's now going to be exposed to ammonia and nitrite which in his weakened state will likely kill him in hours