switching light schedule in middle of a grow

4 weeks into it sounds like it could be risky. If you MUST do it all in one go I would say go with the 24hr darkness to turn things around. OR.. Ease them into it, let them have 12 hrs light 14 hrs darkness until their dawn starts at 7pm. This will take 6 days, then you can switch it back to strict 12/12. Or you could use a larger increment. 12hrs light, 15 hrs dark, will take you 4 days until their dawn is at 7pm.

I don't understand why you would want lights on at night, but if you must do it for whatever reason, I agree with the above post about giving them 24 hours of dark, then starting the new schedule.

Benefits of having lights on at night instead:
- No suspicious sounds of fans, no bright lights protruding from cracks in the doorframe of my closet grow, in the event that I have unexpected company or apartment maintenance.
- More even temps throughout day/night cycle. Gets hot during the day, so it's easier to keep temps down if lights are on at night when the temp is generally cooler anyway.