Honeycomb Moray Tooth Decay?

Our honeycomb moray has black bits growing on the tips of her teeth. We have been treating her for crypt for about two months, and it has cleared up, but because we removed the carbon from the filter to medicate her, we are dealing with this new problem. She was eating normally until a few days ago, and now shows no interest in food. We noticed the black stuff growing from the tips of her teeth. We have done a 50% water change, added carbon back into the system. Ammonia, pH, nitrite and nitrate and salinity levels are OK, but we discovered phosphates are high. We are trying to lower that now. I'm attaching a close-up of her teeth, hopefully you can see what is going on. Any ideas? Thanks!