and Welcome to OB!
I just rescued a mini phal in the exact same potting situation from a Big Box. I noticed rot starting to set in because those things are potted in something that gives them no air circulation, and the quality of that moss isn't the best. You did the right thing with ordering new medium and watering more as phals like it more on the moist side (be careful not to over water, however).
Be sure to cut back any rotting or dead roots (there are videos that can show you how) when you repot and try to get as much moss off as you can. Rinse the roots off and if you see any fungus spray with some physan 20.
You might lose the spike, so make sure to cut that back too. That will signal to the plant to focus on putting its energy to roots and new growth. The plant may be weak, and it may be best for it.
There could be other factors too such as water quality, humidity, lighting, pests, etc! Overall the phal looks pretty good. Keep in mind that spike might also be old, but my feeling is lack of agua fria.