Help with psychopsis, sudden rot?

[Roberta]

I'd trim the rotted part with a single-edge razor blade (clean cut, and disposable) and dust the cut with cinnamon (or powdered sulfur if you have it) Physan isn't going to do much. I'm usually not big on surgery, but here you definitely don't want that rot getting into the rhizome. Better to sacrifice a pseudobulb than to lose the plant. It did get too cold - these like house temperatures - Phalaenopsis temperatures, just more light than a Phal.