Could be your lights, might now be the proper lighting. Also, check Phosphates and Nitrates. I was having the same problem. My nitrates and Phosphates were insanely high. You should be testing those weekly. Your results should be 0.0 ppm for both tests. At most, your phosphates should read 0.5 ppm.
Not enough light? Too much flow? Water parameters? Clownfish trying to host it, thus aggravating it? --- These are what I've experienced that have led to my Goni to be closed up.