24 hr yellowing leaf & pits on Phal....Newbie needs advice

[Amydillo]

I purchased my first large Phal. a few months ago to start really learning the art of orchid growing. In the last few weeks, one leaf has curled and now this big change since yesterday morning. It was repotted in bark by the nursery worker. Has now dropped all but one bud off a second bloom. It is in an East window in a warm Texas bathroom. I use a bamboo skewer to check moisture levels, and it is fine. I'm wondering if it needs to be repotted into a more ventilated pot? Too much sun? Normal leaf drop?
See attached pics, the first two where it lives and then the third pic is 24 hrs later.