Duncan won't open

[MandarinMama]

I've had this one head duncan in my reef for a year now. He has started growing 4 baby heads around the perimeter about 2 months ago. I have him near some xenia, which don't sting. I also have a rhodactis and a clove polyp near him. A frogspawn is not close but is in the tank as well.

I have been battling cyano in the tank for a while. It just doesn't go away completely. After duncan closed I did a 5g water change... its a 20g aio...I changed the filter sock, cleaned the skimmer. I've tried spot feeding with reef roids but he didn't seem to change.

The ONLY thing I have changed is I started dosing microbacter7 for about 10 days maybe. I'm not sure how that could have affected him negatively. The only other coral that is not so happy is my GSP on the back glass. It's not really open so much. xenia is great, frogspawn, zoa, clove, everything else is doing fine.

What is going on?
One pic is today. One is from 2 weeks ago.

 

[vetteguy53081]

Best at mid tank under moderate light and water flow and feed it mysis 2-3x per week

 

[Shirak]

Have you tried running some carbon to see if the softies are putting anything into the water?