Help me not to kill this phal (and avoid stem rot?)

[Roberta]

Phals seem to tolerate repotting while blooming. I'd go ahead and pot that one up, in a well-drained medium. (Like medium bark) Let the roots turn silvery before watering again - the open medium will have lots of air space for that "humid air" that the roots need. Also, all that air will provide an environment where rot (bacterial or fungal) can't get a foothold - with a healthy environment, there should be no treatment needed.