Weeks in flower or weeks left? Sativas can take a really long time to develop, that plant might have been flowering for a month or more, and it'll take several more months to finish. What are your temps like? Keep an eye out for deficiencies, that purple stem might not indicate anything, it could be the cold or it might be a mag deficiency. Those inward curled leaves can mean a few things too, just keep an eye on it. Good luck!