White and puffy? sounds like columnaris (a flexibacter), if the M/P mix doesn't work try binox or furanase, both work pretty well on both true fungus and bacterial imitators.
Oddly enough a quick (less than a second) dip in hydrogen peroxide ( same stuff you use for cuts on yourself) also works very well, if you can catch the fish without further injury, and if infection does not involve the head or gills.