White mold: Are these roots infected?

[chungl]

A phal that I've had for six years has some wispy white mold around the roots. I noticed it yesterday and it wasn't visible when I watered earlier this week. The mold is hard to photograph and is more obvious and widespread in person. Full resolution photos

My biggest concern is that the roots seem to be blackening where they are in contact with the mold. I was hoping the mold was just feeding off the moss, but these roots aren't normally this color so I assume this means they're infected. Should I consider cutting off affected roots to limit spread, or is it better to leave them intact and treat as-is? There are other unaffected roots, but some of the dark roots go right up to the stem.

I plan to repot the orchid, probably switching back to the type of bark that it used to live in. I assume I should rinse off as much of the mold as I can, and I've seen some recommendations to spray the roots with dilute alcohol or a fungicide such as daconil to try to kill the mold. Is this a reasonable plan?

I know these roots are dehydrated and have suffered some damage. I live in an arid climate and used to have this plant in bark. I switched it to moss in December to try and help it retain more moisture, and some of the roots were damaged in the process. There's been progress and it's definitely retaining more moisture. It didn't seem to be too much and it's still drying within a few days after watering, but now there's this mold problem :'( Despite the sad roots, this plant has been growing leaves and flowering once a year.