It surprises me that you're getting yellow water with the oxydators and carbon. Wonder what's going on in there?
I still have leathers shedding, I also tried an orange finger sponge with white zoas, somewhere before me it had been exposed to air and is still sort of alive but still letting go a bit, the leathers part is my fault for adding two cave gobies that constantly re arranging my sand so it is them that have sort of made the tank cycle.