How often are you feeding the fish? What foods?
What are your water params for ammonia, nitrite, nitrate, and pH?
Binox is probably the best med out there for what you are dealing with. I would do the larger water change, and while doing it, try to suck as much of the white fungus as you can out of the tank at the same time. It sounds as if another treatment with the Binox is needed. Do you have a quarantine tank? I am thinking that moving the fish to a tank without the fungal issue may tell you if the issue in the tank itself is causing the fish to remain sick or to be reinfected. Treating them in a quarantine tank would be the safest way to be sure they are responding to the medication. This would also remove nutrient level from the main tank, and give all of us a better idea of how to get rid of the fungus in the tank. Some strains of fungus can be tricky to kick.