What have you got vegging alongside the NL? I have a perpetual grow going so I have plants of all different ages
vegging together. I've noticed that if one plant starts to show sex at 20/4 it encourages the other ladies to do the
same.
The longer you veg the bigger the plant will grow. If plants do start to show sex earlier than you want there's not
much you can do except leave her in veg. Most plants will grow vertically for a week or 2 into 12/12, but the longer they
vegged the less they will "stretch" during the flowering phase.
BigSteve.