Fish dying/dead - Heavy Breathing - Need Help

[apex82]

I have not taken the powerheads out and washed them yet. If they are not better by tomorrow, I will.

Ya I talked to water company today and they have been doing a "flush" in area the past while... however they said the chlorine has not been increased that much. I am using prime and has been fine in the past...

Do situations like this take awhile to fizzle out? It has been two full days since the episode, not sure if they should be back to normal by now? I have changed about 50 gallons of water on a total volume of 95 gallons or so. As far as bio-load, skimmer is rated for much larger tank with a heavy load and most of the fish are smaller than 3 inches. I am not sure how it could be lack of oxygen? I have tons of flow agitating the surface with an open top, is this not adequate? Thanks for all the help and suggestions!

[apex82]

Day 3 and tank looks empty... All fish hiding and not eating except for 3 out of 9. Albeit there breathing is better than 2 days ago I would still consider it abnormal and rapid. Breathing before was large wide mouth rapid gasps while today mouth is staying more closed but still seems like excessive breathing. I am not sure what to do at this point... If everything was better should they be back to normal by now? Or does an event like this take a week or so for them to start eating and swimming around again due to the stress?

I just don't know if I should try more things( more water changes, different powerheads, take fish out) or if water is okay now but it just takes longer than 3 days for them to start eating and not hiding....