Hey everyone My plants are about 3 weeks from seed I was wondering if I can switch to 12 12 light cycle in order to sex them ?
Yes. But Id probably give them another week-10 days. Id also Possibly Up Pot them into a bigger container, if they are in smaller size containers, and taking up all the root space. If they still have plenty of root space disregard. I don't like plant roots cramped/rootbound. At All.
Honestly tho, at 3-5 weeks from seed they will start showing sex regardless of light schedule. If you switch they will take 2-3 weeks to start changing anyways. Then you'd have to wait a few weeks to start revegging. I grow 12/12 from seed until sex and then veg. Yours are far enough along that you'll see sex soon. Wait