The plants need 12 hours of a dark period to flower. The answer to ur question, only allow 12 hours of light per day and make sure they have 12hours of complete darkness.
Rookie grower here.
My advice is not to cut the buds unless your going to bring them back inside under 18/6 or more light (re-vegging)
The next piece is what I just told my little cousin who is having the same issue down here in southern california.... let it flower and hope for the best...
I'm a rookie grower myself... so take this with a grain of salt..
From my understanding, those leaves are crucial and packed full of nutrients for your young plant. I would not cut them off until they look wilted and die.
With that said, the cotelydon leaves curling up wouldn't concern me...
Hey guys/gals... I hate posts that never follow up.... that being said, all 4 plants are fems. Im 3 days into 12/12 and they have all displayed female preflowers with pistils. The part i snapped in the picture turned out to be a funky new growth and not a preflower.
Thanks to all who helped...