Sick Xenia

My poor little xenia is not doing well. On Saturday my warmed up to around 85 degrees. The next day I noticed that one of the xenia's stalks was turning white. It continued all day yesterday and now I have another one on the same rock doing the same thing. The little waving hands look shriveled. In the picture, notice the xenia in the back right. The other corals look fine so far, green star polyp, cabbage leather, and mushrooms. I have a clean-up crew arriving today, and want to make sure that the tank is safe for them.

I tested for ammonia, nitrites, and nitrates. Ammonia and nitrites were 0 and nitrates were very low. SG = 1.024. I am using treated tap water, and did a 10% water change about a week ago. I know, I need to get an R/O unit. I use Instant Ocean salt. My tank is 2 months old, and I have a single Six line Wrasse and a few snails. We are currently battling red slime on glass, rocks, and sand. I do not have test kits for phophates or calcium.

I feed the tank on cap full of Marine Snow once a week. I did zap an aiptasia on Friday with Aiptasia- X. The xenia was in the same vicinity.

 

Xenia, in my extremely limited experience are, are a fickle bunch. One (of two) of mine looked like it had died off. So I raised the alk from 9 to 11. They both perked up a bit. The dead one even started to look alive.......then they both crashed. Maybe I did it too fast. But that was the concensus on the forums, get the alk to about 11 and they should thrive. I just bought a new frag, and as soon as I get my leak fixed, I am going to check my alk and raise it if needed.