Brown fungus/mold Phal roots please help

[cajander13]

Hi my name is Adam and I am relatively new to orchid growing. I have about 20 phals that have browning roots that become dry and twig-like. This only happens on the exposed roots above the surface of the medium. There is also a white fluffy fungus on the undersides of the roots that haven't completely turned brown. All of the roots in the medium are healthy. I have not been overwatering, and even when I bring home a new phal, within a few days the roots start to get brown spots forming on them. I have a 0.9% sulfur fungicide but don't know if I should use it. Any help would be greatly appreciated.

Thanks,

Adam