Hi Dino,
That looks like "Cyano Bacteria" to me. Hard to tell from the pic, however if it gets on the coral, it will definately damage tissue. You can blow it off the coral with a turkey baster daily, however you will need to treat your tank for the cyano if you want to get rid of it, and do your best to find the cause. Low flow could definately be a part of it, however I fear you may have phosphate problems as well? It's hard to say.
I might be wrong, however I would suggest you look into it anyway........good luck, I have struggled many times with this in the past myself. It is very treatable, so hopefully that is all it is.
Kris.