man your tank is SOOO nice, honestly, and the deal with the puffers and other, your taking ALOT of care with them, maybe too much?
imagen if like you got sent to the hospital every time you had a tiny cought of something, thats sorta the same thing, it could stress it out abit, just trust it,
if its only the puffer gettin affected and nothing else, chances are its nothing to do with the tank, just the specimen. you worry too much
but yeh truely spectactular tank, im wondering how you manage to keep an emp and a queen together?
and also, how come the puffer doesnt bother your chromis?