I use a master test kit and the tank is planted.
Well then there has to be a shock to the fish some how. There are only a few things right off. Temp, PH, mini cycle, Starvation from food change, Major stress cause they are not used to things like Sounds, foot trafic, cat or dog, lack of a hiding space, lighting.
If you hit the bottom of this list i dont know what to tell you.