Receding Coral

[RG22]

Went on vacation to come back to one of my corals turning white and pigments slowly depleting. I was thinking that the coral was being bleached but it has been in the same position for months and was doing fine until now. Hammer coral has been receding and it almost seems like the tentacles are getting thinner. I moved the hammer lower in the tank because that also is losing color. When testing parameters getting back carbonate hardness ~7 and calcium ~350. Salinity at 1.025 and temp at 79. Did a water change and calcium is now at 500 and carbonate hardness 10.5. Only 2 corals seem affected and the other 3 are unaffected.

 

[blaxsun]

Any slime/BJD? ie: do the corals stink like rotting flesh?