The leaves, the stems, everything turned a dark shade of purple. This only happened to the ones that got six hours of sunlight (which is normally recommended for white potato vines)--the ones that got more shade were fine. My mother moved them to an area with more shade, and they returned to a healthy color overnight.

We know the solution to the problem, at least, but I'd still like to know what exactly the problem was. Has anyone else had this experience with white potato vines?

(For what it's worth, I'm posting this from California. There's a decent chance this has to with the drought.)