receeding chalice

[Frogfish]

I have a watermelon chalice that has been receding the past week. Nothing in the tank has changed, no additions, no new bulbs or filters etc. Everything else is doing well.

This coral has been in the tank for over a year and more than doubled its growth. Now the flesh at the edges is receding and I am seeing white skeleton.

There are no other corals close to it that could be stinging it.

Suggestions?

 

[roshi719]

I would check your magnesium levels. I have seen chalices do weird things when mag levels start to drop.