Help! Rescue phal all black

[Mercurianmad]

Hi everyone. I rescued this phal from my neighbor about a month ago. I’ve been watering regularly and fertilizing with FEED ME every week, 3/4 tsp for 1 gallon water, rinsing with water the day after, and skipping the fertilizer every fourth week. It’s next to my other phal that’s flowering and happy.

Today I pulled some of the medium back and noticed that despite reporting, watering when medium is dry, and fertilizing plus using an orchid probiotic solution every 21 days, the roots are black and I can’t see new ones. Plus their was some fuzz on some of them.

I’m when I repotted a month ago I trimmed some of the roots with sterilized scissors and lightly dusted the cut tips with a thin layer of cinnamon. Now I see there is so much black on the roots and near the base, I’m not sure how I can keep this plant healthy? I don’t want to stress it out too much. Should I leave it alone and just continue to care for it as I am?