light time?

let's say in the same growin area i have 6 plants that have been flowerin for 3 weeks and 3 plants that are now to the 6-7 weeks of flowering. they both need 12/12 right?

I would say - yes both need 12/12. Sounds to me like you'll just get to harvest three of the plants earlier!

allright because another guy there told me to put the 3 plants that are almost done to 16/8 instead of 12/12 so i wasnt sure..

I'm no expert but if you already started flowering don't go back to 18/6. For flowering the 12 hours (minimum) of uninterupted darkness is the important part - otherwise you risk hermaphroditism or reverting back to vegetative.

They are both in the flowering stage, right?

ALL flowering plants need 12/12...

BUT if they are different sizes, you should put the smaller ones in the center of the room (under the light)... or put them on boxes and raise them...

different flowering schedules, in the same room can be tricky... a light mover can be very helpful in such circumstances...

cheers