Dying colt

[boxerzz]

I have this colt coral for 2 weeks opening up nicely. Then suddenly it stop opening up and stayed shrink for almost two weeks already. It is looking smaller everyday and the foot seems to be receding. What can be happening ?

Parameters :

5 nitrates
8.2 ph
8.4 kH
1.025 sg

It is in moderate flow and under 4x 39w T5s in a 36" high tank and at middle level.

 

[Flipper62]

When you say nitrates are at 5.....do you mean 0.5 or 5.0