Looked like zoa pocks to me.
We had a large colony develop the exact same looking thing and used Furan II to clear it up. 90% of the colony came back in less than a week. The last section I just ripped off and threw out as it was too far gone and I was tired of dipping.
As far as the macro algae goes. No idea, my tangs don't let me keep any.
Good luck.