Fish dying/dead - Heavy Breathing - Need Help

[apex82]

Alright, just changed another 30 gallons so thats puts it up about 80 gallons in 3 days on a total water volume of 95 gallons(almost 100% water change). I took out the new evolution powerheads are soaking in vinegar and replaced with my old koralia 3's. I think thats all I can do and hope for the best...