I see what looks like broken down medium (black particles) in the pot, but not anything that is clearly mold or fungal disease. The discoloration on the root tip also does not look like a fungal problem.

I think people are sometimes too quick to use Physan or other chemicals. I've been growing orchids for 30+ years, I have never purchased or used Physan. Instead of chemicals, I would suggest that you remove the root mass from the pot (should be easy, but probably there will be slight damage to some of the roots that have gone through holes in the pot; this won't hurt the health of the plant). When the root mass it out, run the roots under running tap water to rinse out decomposed potting medium (the decomposed medium looks like potting soil; if in the sink, run the water into a bucket to avoid clogging the sink).

After rinsing, let the roots dry outside the pot for a few hours, then you have a couple options. (1) Remove any remaining old medium from the roots and re-pot using whatever growing medium you like (if you are not sure, I recommend bark-based orchid medium). I re-pot most of the Phals I buy that are blooming into new medium as soon as I get them home, it does not hurt the blooms at all. Repotting is much less damaging than roots sitting in decomposed medium. (2) If you can't re-pot, after rinsing the roots & allowing them to dry (maybe 3 or 4 hours), put the root mass back into the same pot until you are able to re-pot.

Good luck!