DKoKoMan's 150g Reef Tank

[DKoKoMan]

So today I noticed an aggressive brown algae on my live rock and on some of my corals. Some of my Zoas are struggling to open and it's best described as stringy brown algae with bubbles that appear and disappear. I checked PO4 which is 0.15 ppm (high I know) and NO3 approximately 20-40ppm (API test kit). I am ordering a new nitrate kit as it's very tough to distinguish the difference in colour shades.

The only thing that has changed in the tank is the intensity of my led lights which I ramped up 20% and carbon dosing via reactor with biopellets. I took a quick photo to show one of the areas that has this brown algae present. My white gonipora is starting to get covered in this brown algae preventing it from having plump extension.

Please Help!!' No idea where to start with this and don't want to start chanting a bunch of things. Haven't had this issue before as this algae seems to want to cover my sps, LPS and Zoas.