That happened to me. I had bought a red sea max with all the livestock from a guy and moved every thing. It was all great for months then the heads started to drop off till they were all off so I removed the branches and it was so fragile it broke apart. I think it was because the guy never did...
Try algaefix marine. It is safe for all inverts and really works. Also get a sand sifting goby. They like to sift the sand through their mouth and eat that stuff. Algaefix really works.
I have a red sea max 130. I like it because it isnt too big. Though I would like to get a 90 gallon one day. But the RSM has a protein skimmer a sponge for water polishing and is attractive to look at. The main thing is to do your water changes on a regular basis. That will keep your nutrients...
Do you have protein skimmer? Your nitrates are too high. Keep doing small water changes and don't overfeed. Also you have to target feed some mushrooms and most anemones.also, the water changes will raise your ph and calcium plus lower nitrates. Good luck, carol