switch to a 12/12 lighting cycle, your going to need to flower more than 3-4 weeks(counted from when the first flowers show after flipping to 12/12 if you switch b4 the plant is mature, if the plant is mature b4 you flower it you count from the first day of 12/12) probally more like 10-12 weeks for indica, sativas take up to 12-14 weeks