Coral Banded dying

Well I don't know what happened at all, except maybe he didn't eat much during the times I feed the tank. My coral banded which I've had for a month is dying it seems. He molted 2 nights ago (the night of the 24th) for the 2nd time since i got him, I noticed him late last night barely hanging onto the rock. I removed him and placed him in a container with an aerator. His antennae are still moving and he is still pumping water over his gills but his shell is not hardened at all, which it should be after over 24hrs, and he is otherwise motionless. I direct feed him after I removed him from the tank but only ate one piece of frozen mysis. I have no idea why his shell hasn't hardened or why he is dying. Up until he molted, this guy was very active and territorial, sometimes chasing my clowns. kinda funny to watch because the clown seemed to antagonized by being just out of reach.



Cal - 450

Mag - 1280

Alk - 9.8 dKh

Ammonia/Nitrite - 0

Nitrate - 0

pH - 8.0

Phosphate - 0

Temp - 77