Same here my tanks is full of acros having this issue. So discouraging, since it makes polyps look horrendous. I had this in the past, and stopped. Putting 2 and 2 together, i was carbon dosing when i had this in the past, and im carbon dosing now (Aquaforest NP-PRO-PRO BIO S). I have stopped it completely, and see if i have any changes. Any help from would be greatly appreciated.