possible stress too the plants
have you changed any lights
He says he's outdoors. lol
did you start them inside and then put them outside? if this is the case, then they could be revegging, flowering outside starts more or less around the end of august through october. A common problem is when a grower takes plants from under 24 hour lighting and throws them outside, it throws off the plants cycle, and it starts flowering, Then it has to reveg which can take some time. I know from experience that plants will put out single bladed leaves after starting to reveg or sometimes even after a clone is taken.
We need more details on whats going on to accuratley help you, also pics would help