I'm not sure what the orange algae is (I would not assume it isn't some type of cyano from what you report, but it could be some type of diatom or dino (the worst possibility) or something else entirely,
FWIW, I do not believe
imbalances in the N

ratio cause excessive algae growth problems. A sufficient amount of both allows algae to grow, and an insufficient amount of either (or any other potentially limiting element) will reduce or stop its growth.
IMO, it is unlikely that dosing nitrate is ever the solution to an excessive algae problem, except if the "algae" is dinos, and in that case, it is not that the dinos thrive at lower nitrate than high, but because other organisms outcompete them for something else (such as iron). That said, nitrate dosing may be good to do for many reasons, even if you have an algae problem. Most important is to prevent dinos and feed corals.