My guess would be different pheno's, different times. You do your part to feed them and water them (not over or under), then you have done what you can...besides LOVE..
(And adjust your lights and keep your buds OFF them....sigh), my best cola on Abbie touched the sun just a bit, hope only the little curly guard sugar leaves were damaged. And some pistils of course...
You know, I would of really been bummed my first grow...but you learn very quickly you are human and if you do the best you can, most of the time it is enough lol.
brother.