Hey Fruitgrower, how are you.
Its been a while ago.
I see you made it to the finish👌🏾
To answer your question, the buds you talk about was probably half dead already and didnt get any nutrients for a while.
The plant does this to prevent that everything dies of so it lets the weakest things go first.
I thinks the broken stem is the main reason.
Good luck on your next grow my friend, and always keep on growing.
Peace 👍🏾