Those hermits and snails are getting an all you can eat buffet.
The hermits, Scarlet, I am guessing, will eat all of those algae quite fast, along with the blue ones. I dont see why your tank is so plagued, unless your fish are crapping as they eat. Thats some nasty punch.
Id just give it time, if anything pop a bag of carbon crystals to ease the growth of the algae, and cut back on white light. Actinics are ok.