Duncan Coral Base Receding

[Lunar Mike]

Hi, my Duncan has had some receding/dying off recently at the base, I think. Looks to be getting worse but cannot tell. It appears to be fine and growing another head except for the flesh dying off at the base.

Is it normal skeletal growth or something possibly bad? Water checks out, temp is 78-79. I have been moving it around lately trying to find a permanent spot to glue.

I think it prefers lower flow and less light based on how it looks or is opened up at different spots in the tank, not really sure though Should I start feeding regularly?

My tank is a Nuvo 16 with a Kessil 150 Ocean Blue, pump is upgraded/larger(too big?) and has more flow. Any help especially if you have/had Duncans would be great.

Pics aren't the best.
"I'm am learning"

 

[Lunar Mike]

This was shortly after I got it and it was closed up. Kinda looked white at the base and that is exactly where it died it is dying off.

The other pic is how it looked in lower flow and the change of the base is more visible.