Help identifying stem rot on struggling phalaenopsis

[estación seca]

15C / 59 F on a routine basis is pushing their temperature tolerance. Plants may survive but from time to time expect losses.

[camille1585]

Even 10-15°C on occasion can be pushing it depending on the Phal. This summer I actually had cold damage on 2 Phals outdoors when the night temperature dropped to around 12°C. Needless to say that I brought them indoors after that!