sounds like you have autoflowering plants.wich means you dont have to change the lights to 12/12.you keep the lights on 18/6 thru the whole grow.do you have female seeds?
Autos are quite different than regular plants. They are crossed with ruderalis which enables them to flower without taking the lights to 12/12. They will also finish faster, but you cannot clone them, and you will get less quantity and quality.
Keep the lights on for 24/7 for several weeks. Then I would take the lights to 20/4 and let them finish. Most autos take 9-12 weeks to finish.