I have a 55 gallon tank. I got it from a friend with a brittlele star, a lobster, 4 damsels, and a small sea urchin. I added a mushroom and a soft coral. 3 damsels died, the urchin died and the other damsel is sick but is eating and seems to be doing better. Last night I found small white living oranisms all over the glass. Is this bad? Help!!!