That coral is suffering from RTN and its toast , Find another LFS if they sold that junk. Hell I'd give that away if it was in good shape if it was in that shape Its throw it away . Sorry buddy you got sold a dieing frag . if they charged you more then 5.00 for that in a perfect healthy condition that would be about right. Its nothing wrong with your water from what you posted you have any other SPS corals in the tank ? Tell me what lights do you use and the temps are getting a little higher then I'd want at 82 or 83 ? I think you posted . As for light accuilmating ? never worried about it with any sps coral myslef if its healthy and grown by someone who knows what they are doing then it was under proper lighting and can take all you give it . Any SPS coral's we would send out put them under a 400 to 1,000 M/H and let it be , You just got took with that sick coral they should have never had it for sale , I see signs of cyano on it now ..