It is dying., sorry to say that and most likely won't make it.
BUT, please don't toss the skeleton away. New babies will likely to grow on the dead mother plate. Actually, that is how people aquaculture plate corals. they kill the mother so that new babies can grow on the dead mother.
still need to post levels.
Took longer than I thought to get these. I was told to start adding "reef builder"
Nitrate 2
Ph 8.2
Alk 6
Cal 400
Mag 1250
the alk of 6 would have done it
you might read up on two part dosing, (less expensive)
others should chime in, but I think it is just sodium bicarbonate?