coral closed

all the zoanthid polyps are closed on my zoanthid frag. Other animals include a blastomussa frag, a citron goby, a margarita snail, a Mexican turbo snail, and three nassarius snails. The blastomussa is fine. Here are my parameters: Nitrate: 20 ppm Nitrite: 0 ppm pH: 8.0 KH: 180 ppm GH: 180 ppm...