I added this yellow fiji to my tank about a week ago. It has been doing great until today. It seemed normal at first, when I turned the lights on this morning it seemed fine, polyps came out like normal, but now there is a dark spot on the right hand side of the coral, and it seems bunched up around the dark spot. What is wrong here? 
Im testing the water right now, I will give parameters as soon as I have them up to date.
Im testing the water right now, I will give parameters as soon as I have them up to date.