Most fish, especially juvenile fish will act up when stressed out from a change in their environment. This is a given.
But why all the talk in this discussion about gill flukes?
Gill flukes multiply like rabbits, and it doesn't take long before they spread to every fish in a tank, it's not like only one or two fish become infected. Gill flukes are also one of the easiest parasites to spot in a fish, as once they begin burying into the tender part of the gill tissue most fish go hog wild, flashing & scratching non stop. Due to their reproductive cycle you typically need to perform two 7 day treatments , with a gap in between the two treatments, and salt does not eradicate gill flukes so in your case cheon there clearly weren't any gill flukes present in your fish.
Also, as every supplier knows, once a fish leaves their facility there's no telling what the hell is going on in the tanks those fish are ultimately being placed into. A young sensitive fish with a young underdeveloped immune system will usually be the first fish in the the tank to show problems, if/when any type of problem exists, be it water quality issues, or something more serious. Simply adding a new fish from the LFS to a system can create havoc if that new fish is packing heat. The bacteria and/or parasites from a single fish can linger in a system for weeks, only later surfacing when opportunity knocks.
I'm not trying to nit pick here, I just found it rather odd that someone in this discussion was pointing fingers at the supplier, when in this situation it seems to be a pretty clear case of operator error. That error has been corrected, and now all one can do is hope that the damage wasn't permanent.