help when to put on 12/12 ????

hey all im currently growing blue mystic fem (nirvana)
they are 30 days old from seed 29 in pics below as this is my first grow i was just wondering when do i need to flip them over to 12/12 I would like a to get a decent yield per plant and i have a 250w mh on them atm i can add more lights i suppose if needed just looking for some adive

You can flower anytime you want from vegetation. Its up to you really if you have size limitations and how patient you are if you want to vegetate longer to increase your chances of getting larger yields from small number of plants.

u can start once u see preflowers or alternating nodes, but u can also veg for as long as u want

What they said........
But i wouldnt flower with the mh, need hps.

you can switch whenever. the plants will double maybe triple in size. so if you are short on space most people flip pretty early. if you have alot of space i would let them keep going.