Cannabis is an herbaceous annual, and as such it times its life cycle by the length of darkness experienced. Hormones that build up each night cycle, reaching a tipping point around 11 hours or so of continual darkness, is the mechanism by which it recognizes the onset of fall and triggers itself to finish its life cycle. Sorry they didn't get as big as you wanted, but on the bright side, they'll really blast into flower phase now! In fact, with such a long initial darkness period, you may well see a foreshortened 'stretch' phase, and an overall shorter flowering period.
I recently tried to reverse the life cycle of some plants of a friend. The results were disastrous.
