I have 2 bubble corals in my tank, 1 green and 1 a light purple. The green one was doing fine, both were eating until 1 day they wouldnt eat. I feed my corals once every 2 weeks to a month. The green bubble coral was dying fast but the other one was also dying but not as fast. The purple one lost 1 mouth but the green was basically and no joke 99% gone. I just left it in there and a couple months ago I saw it coming back. Same as the purple one, the purple is back to how it was when I bought it and growing. The green one on the other hand is slowly coming back since it can't eat. I started to see 1 bubble and now theres about 10 bubbles. I noticed that in the skeleton, it lookes like a small nem in there but it starts growing bubbles out of there. It is coming back but I dont know why it almost completely died and then its coming back. Both are in the same place on the sand with low flow and medium to high light which I did light acclimate them. Sometimes corals are tempermental, there is a local seahorse breeder here who has a plate coral that looks like it is completely dead in one of his tanks but he showed me how it keeps spitting out more plate corals and once they are about a quarter size, he frags them off. He has about 4 growing on it right now the size of dimes but the mother just looks dead lol.