Moderate flow and moderate lighting. They are encrusting so they need calcium. You should post your tank parameters just because it may help determine your problem. Make sure to include alk
, calc, mag, and phosphate if possible. Also what if any supplements do you add to your tank? Over the years I've only seen that kind of deterioration in good water parameters when there is way to much strontium in a system. Imo
it always seems like polyp corals are the first ones to show signs( plays, zoos, star polyps, and encrusting gorgonians which is what you have). Since your other corals in your pictures appear to be healthy I'm thinking that's not the problem. Also how long have you had them and what steps did you take to acclimate?