I figured out what happened. I had my tower heater plugged into a light strip. It was kicking on and then tripping out constantly all night. So the heating element got hot, but the fan wouldn't blow or oscillate. So I believe it just cooked the stalk of that plant. This was a couple weeks ago. I tried to save her and she's in flower
Glad you figured it out and she recovered!
It’s almost like something was poured on it. Any issues with direct heat? Any signs of pests?