I think you would have been better off keeping the lights on and extending it an extra half hour at the end. I don't think them coming on an extra half hour early would harm them even if you didn't give them a full twelve hours of light that day. Since they were in darkness, and you turned on the light, and then returned them back to the darkness stage, hermie is a possibility. I don't know if doing it one time will bring you seeds though. Good Luck.