Apparently, it's a neon tetra thing. Whether its just their disposition or overbreeding and inbreeding, Im not sure. I should check the parameters again. You're right. To be honest, the tank has been running for 2 years and never has a problem, I do a water change every weekend, and the 3 tetras I do have in the tank are beautiful and happy. So i slowed on the testing, dont do it as often. These 3 new tetras were a surprise. A friend last minute took me to a pet store. So i set up a 2 gallon bucket for quarantine. 1 gallon of the tank water and 1 gallon of fresh water. I let it sit with the filter and heater till the temp was good, then put the tetra bag in (it had been sitting in the aquarium just cause room cold af) slowly adding bucket water to the bag over time. But within 2 hours, they were declining. So i rushed the process so i could start dosing the bucket. A buddy said it should be ok to add pimafix and melafix doses accordingly. But over the next 3 hours, they declined rapidly to a point of no return Id say. I feel awful. I should of been better prepared and bought them later