I am having a small localized breakout of algae (see attached picture) it very localized to the coral in the picture. it brown and I am able to pick it off with tweezers to some extend but can't figure out how to get rid of it. The rest of the tank look fine. my levers are very good Nitrite 0, Nitrate 1.6, phosphate .19 (is that high). Any help would be appreciated.