Coral base brown color

[NewbieC123]

I have noticed my duncan and hammer coral are developing a brown color at the base. They have been retracted as well. Any insight?

 

[Formulator]

What are your water parameters including nitrate and phosphate?

 

[Wandering Albatross]

I have the same problem, but I have 2 hammers on the same frag, and only one is darkened and receding like this, the other is fluffy and the base is creamy white. The receded one still has good polyp color under blues.