Originally Posted by headshake
how many nodes did the plants have before you switched them to 12/12? were they from seed?
cannabis is sexually mature from seed when the plants have opposite leaves. many call them opposite, although this isn't the the correct term. if you notice, when the seedlings are young the fan leaves and branches are coming out directly across from each other, or opposite. as they get bigger, they start to get staggered, or alternating. once they start alternating the plant is sexually mature and can be placed into flower.
also, you want one plant per pot.....period. the roots can become inter-tangled and one will suffer while the other strives usually.
good growing!
-shake