Sunset monti I have had in the same spot for months growing like crazy turned to this on a couple days. Only thing that I changed in a while was iv started dosing fuel and feeding Oyster eggs when I noticed it going a little pale
Look likes its bleaching, mine is doing it too, i started seing white spots where the orange is, but i had it up high and the lights might be bleaching it, i still have polip extension, i read somewhere that it could be potassium and or strontium, but dont have any test kits to check, oh and look for pest on or aroud coral, might be monti eating nudies, lol
Looked for pests dont see any yet, makes sense I did add a little lugiols for the first time in awhile so I guess ot could have been that? Would it still bleach if its been there for a couple months same lights and everything?
50/50 my friend i have brought corals back from the dead and killed corals that where thriving, lol anyways, try not to do anything to the tank thats out of routine, like change salts, change bulbs, add anything except for cal , alk, and mag or course, see what happens, good luck