My xenia normally grow like weeds in my tank but lately they've been not looking so good. They start turning brown at the tips and it slowly works its way down the stalk to the base. Sometimes the base turns white but not always. Usually they get over whatever it is and they're ok, tho what's left is tiny compared to what was there. This only seems to happen in one area of the tank, the rest of the tank is fine and it hasn't affected any other corals. Today I noticed one xenia stalk that was turning brown yesterday is pretty much a pile of goo today and I doubt it will be ok like the rest. What is happening to my xenia and what do I need to do about it? Please help! All params are perfect, I run 2 T5s and 2 VHO T5s. Temp is 84, salinity is .025. I have several mushrooms, a pagoda cup, leather coral, a sun coral, a frogspawn and a sponge in a 120gal tank. The pagoda cup is the closest to this xenia but not touching and none of the other ones are affected.