All fish dieing

[LionfishJW]

I feel the pain with you.

I had a few fishes dead after upgrade from an old to a new tank. Certainly, the migration gave them stress.

Any disease from any of your fishes should have killed all other fishes in the other tanks under the same system as well. This is the part puzzling me... Unless, the system has some sort of special treatment not suitable to your fishes but good for the others.