I've had my system up for about 6 months now. Lots of big Bok Choy, Rapini grew in fine. Shishito Pepper plants sprouted a few leaves then just stopped and i got a big head of swiss chard. Plants seem to be growing alright until about a month ago. About 2 months into the system fish started dropping one by one. Never more than one at a time. I use RO water and add a small amount of water conditioner. I did add some iron chelate that is branded for aquaponics and says safe for fish. My ph is a bit high once estableshed in the system, around high 7s low 8, but when measured before adding to tank it is closer to 7. Ammonia, nitrates and nitrites measure all around 0. I'm now down to just 2 snails in the tank and no fish. I was for a short amount of time adding some aquarium salt to water adds which i realized was a problem because it was all for evaporated water additions so i was salting too much. I took out 75% of the water and replaced with ro water, and a week later got a few more fish which lasted about 2 weeks. One of the snails is from the original stock and has been in there for 6 months and growing and running around the tank plenty. Any ideas why all my fish are dying?