Hammer coral not opening and losing tissue...

[twychopen]

Again, I am new to this so I am reading up as much as possible. I have a hammer coral that didn't open up today. It also seems to be giving off clear/white tissue or slime. I checked the water late last night and everything seemed to be normal.
Temp 78.9
Salinity 1.022
pH 8.2
Alk 2.72
KH 7.6
Ammonia 0
Nitrite 0
Nitrate >20
Phos 0
Calcium 340

I don't have many corals in there at all, in fact these were some testers after my zoas quit opening a few weeks ago. The fish, crabs, snails are all doing fine. Any suggestions?

P.S. I did add some pre-cured live rock (15lbs) on Saturday, but they were fine saturday after and on sunday. I already have 50+lbs of live rock and the system has been up for about 2 months. I checked the water yesterday and everything was fine. No spikes or anything since I added the rock Saturday.