Clownfish acting strange...

Hi!
Last week I added a clownfish to my tank, which has been running since early
September. I have had the water tested by LFS and also test SG and Ph myself regularly. I add bIonic calcium supplement ever 1-2 days as needed and feed the coral Marine Snow every few days.

12 gallon bio cube
approx. 11 lbs live rock
SG= around 1.22
Ph:7.8-8.0
temp: 78-80

The other night I fed my clown some frozen brine shrimp, added the bIonic according to directions, and then went to a party. When I got home the clown was stuck in the water current near the filter and floating on his side. I checked the Ph and SG and everything was as it was when I left. The next morning he was fine, but there were a few extra white spots on his tail, which had a tiny piece missing a small white area on it when I brought him home from my LFS -- he was in a tank with a bunch of damsels and I thought he had just been nipped, but now I am thinking maybe it is something else?

In addition to the clown being stressed I also had some mysterious coral type things growing out of my live rock that shriveled up that night -- they look sort of like very thin pinkish white q-tip shapes with tiny hairs growing out of them. I had a whole colony growing and only 2 are still there now. Hermit crab, snail, tiny anemone and feather duster corals are all completely healthy and thriving. Any ideas?