I don't understand what you want to do.... do you want them to flower? Because they will flower now that the days are getting shorter...12 hours of sun a day is plenty for cannabis....sometimes a full on sun for days during a heat wave is too much .... I've had big plants grow in half sun half shade for a whole season and do fine.... they are a tropical plant, not a desert plant, and grow in the shady rain forests well. I would only worry if stretching is a problem and they would get too tall for ya.