Cynarina help

Anyone want to help with giving me some advice with my cynarina. Its in a low flow area. Its in the bottom of the tank. And its just getting worse and worse. Calcium 400 magnesium 1500 . alk 9. Ph 8.2 nitrates 5ppm 0 nitritis and 0 ammonia. I was feeding it shrimp n reef roids twice a week. Only major change ive done is upgrade tanks 3 weeks,ago. But every other coral is fine except this one