Duncan coral losing skin at its base

[Jé123]

Hello, since a few days, I have noticed my Duncan coral lose a bit of skin at its base. All my parameters are fine and the coral itself looks happy and is open and the coloration seems ok. Is it normal? This part of the coral is shaded so that might explain? Should I worry?

 

[Reefer40b]

Looks ok and healthy

 

[Jé123]

Maybe the angle on the photo isn’t good, here’s the other side which is worse