Need some serious help for my duncan colony

[Acan ninja]

In the last 2 years my duncan went from a single head to a nice size bush of heads to having all its color but no tentacles. i don't even think it's just shrinking up i think there completely gone. i harbor a whole tank of other corals that are doing extremely well but this duncan is a mystery it will no longer eat i don't think it can i've tried moving it several times my tank is completely automated so perimeters stay pretty stable i just don't know any help would be appreciated

 

[Mark9]

Those pictures are tiny.
My Duncan hates alk swings, have you checked yours?

 

[Acan ninja]

my alk has been pretty steady at 10 dkh it on a doser that pumps 1ml of solution every hour my calcium when on a wild swing lately though and is coming back down its about 450 ppm now magnesium is about 1400