Focus on ......the water.
The two factors that concern me most are your KH at 1 and your Nitrate at 0. Your Nitrate should be low, but not at 0 imo with an ongoing tank. Your KH is on the precipice. 17 ppm (1 degree) lower with your KH and you’ll have no buffering for PH issues/crashes. Imo, before fish can be successfully dealt with, the water has to be stable. Others may disagree, but that’s my take on it.