i have a 40 gal Acrylic tank which is actually 2-20gal towers connected by 2 6" tubes. For the past 3 months, I have slowly been losing my soft corals. The mushrooms, button polyps, and zoanthids are all okay. I lost my golden hammer, and clove polyps completely. My green hammer was doing well until a week ago. The trumpet coral is beginning to close up and is losing color. Water tests are pH 8.1, Nitrates 20, Nitrites 0, Alkalinity 10 dKH, Calcium 470 ppm, Salinity 1.024, Temp 78.2, Magnesium 1200 ppm, Ammonia 0, Phosphate 0.008. I am not adding anything for calcium, as it is a tad high. I feed Rotifers 2x/week and Mysis shrimp 5x/wk. Fish include a pair of black ice Ocellaris, a pair of PJ Cardinals, A coral beauty, a chalk basslet, pair of neon gobys, pair of fire Shrmp, pair of cleaner shrimp. The tank has been up and running for 3 years. When the corals first started to die off, we saw our Atlantic Pygmy angel picking at them so sold him. We have looked at night and have not found anything else picking at them. A month ago, our Salinity had went down to 1.022 so took a week to gradually bring it back up to 1.024-5. Lighting is with Fluval Marine LEDS. We have 2 Fluval Powerheads running that were rated for a tank 3 times the size of ours. We are running 2 Fluval 306 canister filters and a Fluval Protein Skimmer. We do 10-15% water changes every 10 days to 2 weeks. Does anyone have any advice or ideas as to why the corals are not doing well.