There's the problem I do believe, about 3 years ago I goofed and lost track of how much stress zyme I put in and it was too much and in about 3 hours or so after disaster hit, as fast as I could pull fish out of the tank others were dieing, out of 23 fish I had 10 casulties and it was right after I had did a water change and added it
I really hope that's the rootcause, atleast I will be able to fix the problem. I will quit using stress Zyme. Should I also carefully measure how much dechloronator I am putting? cause I usually put a cap full everytime I do a water change (approx 30 gallons) and a capful is recommended for 50 gallons.