dang lost my TCK sour polyp, completely RTN in a day
Been there. No fun. Is your alk still rising? I had an Acro start to RTN when my nutrients plummeted quickly, so in my experience that alone can definitely cause issues. My own theory is that when nutrients and alkalinity start moving it weakens the health of the acros, and then they succumb to bacterial issues.
Obviously another suggestion is running an ICP just to make sure nothing wacky is in the water.
IMO, dosing ammonia is better, but certainly also more complicated since you do not want to add much at a time.
I hate sounding like a Triton fanboy, but I have come to trust their products, and especially their dosage guidelines. If you want to try ammonia, NH Alpha product works really well. The best way to dose it is to send in an NDOC test which will give you a guideline based on the nitrogen levels in the tank, and they can then give you specific dosing guidelines. However given your tank size a reasonable starting dose would be 0.2ml per week. That’s pretty conservative and won’t fix nutrient issues overnight, but move things in a better direction considering you’re fallow. It might be a safe way to dose ammonia rather than winging it since home test kits aren’t really great at monitoring ammonia and overdosing would be bad.