Hi, so i got this african milkweed from home depot a few months ago, its only like a foot and a half tall and is fine in the pot its in for now. I noticed this morning that one of the stalks has just decided to peace out of living and rot. I dont know how long this has been going on without me noticing, but if i had to guess i would say a week or two? Its weird because its still green and the rest of the stalk is fine, but the base is mushy and i can put my finger through it if i wanted to. It started falling over this morning and thats how i noticed. What is this, and what do i do?