Yeah, these guys are right, I didn't look at your nutrient levels. That PO4 level will always bring on cyano, at least IME. Or it provides a great environment for it. ChemiClean is what you use to treat cyano, or erythromycin, but that will not keep it away. GFO, or get a 10 micron filter sock and some Phosphate-E from Brightwell Aquatics, or lanthanum chloride, and slowly drip it into the 10 micron sock. Or make a lanthanum Cl reactor.
You need that PO4 level to come down; are you feeding a lot? I bet it is coming from the foods you feed. Flake and pellets always increase my PO4 levels, frozen foods from places like LRS or
@Reef Nutrition are awesome to keep the ability to feed a lot (anthias, other fish that need multiple feedings/day), but keep nutrients down and fish healthier. Anyway, just get the PO4 level down any way you can. If you can do it quickly, meaning you don't have a lot of corals that would be upset, get some lanthanum chloride, same thing as Phosphate-E, use that with some good filter material, get some PhosGuard which reduces phosphate levels quickly, and get a GFO reactor if you don't have one already and just start using it. It's worth it. Also try to set up a refugium in your sump, or you can get Gracilaria for your DT, which reduces PO4 more than other macroalgaes, and looks great too.