Airstones don't raise ammonia, what they can do is drive off carbon dioxide, which raises the pH, which in turn makes the ammonia more toxic....but you shouldn't have an excess of CO2 in the tank anyway. I think what you heard was during acclimation, when fish are in a bag of water after shipping, the pH is really low and the ammonia is really high. You put an airstone in that, and you'll kill the fish right in the bag....but this is only an issue when acclimating, not in regular tanks.
Still, as
@artieg1 said, you need to manage the ammonia to near zero, and low oxygen can be a huge issue if you are dosing with prazipro.
Have you been getting your fish all from the same dealer?
Jay