Duncun dying?

[20clowntown]

Hello, I got out of the hobby about eight years ago and recently got back in. But I don’t have much prior experience with corals. I have a 20-gallon long tank now, about 3 1/2 months old. I have had the Duncan in the tank for about 5-6 weeks and it has done great so far and it has started growing a new head. He always looks big and happy and then today he looked like this. Is this his skeleton? Is his flesh gone? I am not sure if it is dying. It looks like it has a bit of white something coming off. Please help!

Perimeters:
Salinity: 1.025
Ph: 8.00ppm
Ammonia: 0.25
Nitrite: 0.0ppm
Nitrates: 75 ppm
Phosphate: 0.0ppm
Calcium: 450 ppm
Alkalinity: 7.5ppm
Magnesium: 1485

 

[santeeeyyy]

The PH and Alk seems a bit low, I know duncans are weird have you tried feeding yours? When mine receeds it gets fully engulfed in its skeleton

 

[20clowntown]

The PH and Alk seems a bit low, I know duncans are weird have you tried feeding yours? When mine receeds it gets fully engulfed in its skeleton

The Alk was at 8.5 10 days ago, is that enough of a drop to be a swing or harming?

Also the sides of the stem part use to be a brown colour and fleshy now it looks like
White bone, I don’t think there is any flesh and it has been withdrawn all day with some stuff coming out. Is it dying?

 

[santeeeyyy]

The Alk was at 8.5 10 days ago, is that enough of a drop to be a swing or harming?

Also the sides of the stem part use to be a brown colour and fleshy now it looks like
White bone, I don’t think there is any flesh and it has been withdrawn all day with some stuff coming out. Is it dying?

brown? maybe brown jelly disease? unsure if they get that but it sounds like how my hammer polyp died. check your ammonia