Similar thing happened to mine, dip it in tank water mixed with iodine for 20 mins and lightly brush that necrotic tissue off. Repeat in a week. Mine lost a decent amount of tissue and has now totally recovered, I wouldn't frag it apart just yet, it should recover after you treat the bacterial infection. I keep mostly all SPS and a few Lps as well, it isn't starving,it has an infection. This is my only soft coral, they look beautiful and many guests really love it.