OhNeil1969
Aquarium Advice Addict
I'm not envious of your position right now. I hate when something happens to my tank/fish without an obvious reason. Having said that, I really think your best course of action is to be patient and continue to monitor your fish. There are so many different things that could be going on that it can get a little daunting trying to solve the problem. I did think of one possible cause that may or may not be fatal. If the pH of your lfs's was significantly different than yours and you did not acclimate your fish prior to adding them to your tank they may be suffering the effects of that sudden swing. That could explain their difficulty with breathing. If they're hardy, they may pull through.