Thanks for the link and comments Reefing. Tank has 150w LED’s. I did read about oxygenation problems as a possible cause but power heads and skimmer are working fine. My salt was a little low when I did a WC a week ago, but the rest of the tank looks fine. About a month ago I started feeding the tank live food - grindal worms - but I don’t think that’s the problem. As a side note, fish scarf up those worms…
I don’t dose anything, been using Reef Crystals for years. Maybe allelopathy? The coral is about the size of a cantaloupe and I forgot that I did relocate it recently - higher up and more central so it’s getting more light. Seems though that increased light can sometimes actually solve the problem.
Will just wait and see and update as needed.