Yellow looks like sponge to me!
I'm not sure if the brown stuff is detritus or algae...Is it actually growing on the rock or is it floating around? If it's growing it's likely some sort of algae. Algae will grow if there is too much nutrients in the system or you are set up under lights that encourage algae growth. Make sure you're not overfeeding and ensure that you have an adequate clean up crew and enough flow so most particles in water will not settle to the ground and will be picked up by the protein skimmer