If you look at these girls closely, you'll notice on the left, the start of flowers ( I call them popcorn ) . But, the little girl on the right has none. They are all Chemdawg, all popped the same time , all the same nutrients etc. I haven't stressed them that I know of and there are no signs of Herming, No start of seed pods. 

Out of 5 plants , two of them have no popcorn yet. Should I worry ??