Frog Spawn Coral Dying?

[reefer403]

My tank has been up and running a couple months now. Everything seems to be flourishing. Today I noticed 1 of a 2 branch frog spawn coral was comp[leted retracted, and I could see the calcerous base. It seems that the coral has been releasing its own fleshy chunks. I used to have a colony of trumpet coral a while back in a other tank, and one of them died and it is the same "look" of calcium base. Parameters are good, nothing unusual.
I kept it at the bottom of the tank in a mid flow area. Anyone have experience and maybe could provide insight? I hate hate hate nopt knowing what I have done wrong as I would like to avoid in the future. All I know is everything seems good and it had flourished in this spot for 6 weeks. This was an overnight occurence.

Thanks,.