Plant still not flowering

Hi guys,
I'm new here, i hope that this is the right section of forum to ask this question .
I have 20 little plant shared in 2 growbox under 1000w mh (hps for vegetative stage) that don't want to flower.
I've already set 12/12 hours more than a mounth ago but still not streaching or flowering...
The temperature is aroud 22/23° and the humidity is set to 50%.
The palnt are beatiful and and look very well with no lack or defect but still not flowring and i dont now why...
I'm using atami ata organics line to fertilise and following the right schedule.
I've red that i can set the light to 11/13 to help them become flowring, it's a good idea? It can works? Have you got any other idea to force flowring that plant??
Pleaase help me!!!

How long did they veg for? I use hps for flower mh or fluros for veg. I would keep it at 12/12. Are you sure there is no light getting in during 12 off time.

pics please.. and yes, MH for veg, HPS for bloom..


"I'm using atami ata organics line to fertilise and following the right schedule" >>> whats the nute schedule you're following?


first grow? 20 plants?

What strains are you growing? Some Sativas will take a month or more to show signs of flowering.

Yes you can do 11/13 which can help speed up flower initiation for some varieties.

Yeah normally MH for veg and HPS for bloom. Although you can grow either for whole cycle.

Maybe the change in spectrum has confused them and delayed flowering.