Update: After about 10 days of puffy ankles, they went away and have not come back. Hooray for that.

My two main hypotheses for the cause are dehydration and inadequate protein intake. Hoping that's all it was.

Still waiting to see a doctor. After searching the regional medical groups for days, I finally found one that is accepting new patients (Stanford Family Medicine). The earliest appointment I could get was October 9th.