I have a problem. On last days my plants grow a lot. Like they are touching lamp! I switched fotoperiod for 12/12 around 2 weeks ago. Preflowers are visible on them.
I don’t know what to do? Should i cut main stalks?
Flop the tops (do not cut off). You sort of ‘gently crush’ the stem a little and lay the upper section horizontal. That will buy you some extra height for further bud growth.
Without some pictures I can’t really make ‘guesstimates’ as to where etc.
I constantly run out of headroom lol; you’d be surprised how close your tops can come to the light before they start to burn. Some of them just fatten up nice- just make sure you have airflow between the light and tops.