Ist it necessary to wait to send to flower

The only thing that will set you back is if the plant is not mature. Photoperiods will only flower once the plant becomes mature at about 4 weeks. If you grow a seed at 12/12 it will not flower till later in its life despite it getting the longer nights that initiate flowering conditions for the plant. Should be fine at 4-5 weeks I would not do it before this though. Good Luck!

Yeah, I'd say so! They are nice and low and looks like you could even veg them a little longer if you wanted because you have them low enough, but you could also flip them to flower soo too as it looks to be filled pretty nicely. Better to be on the safe side, and have extra room until you know how much a particular strain is going to stretch, then you can push it a little more for better yield without fear of the plant growing too close to the light. Good luck!

I would say your good to go. Flip em.

Yeah your good to go.

Your screen looks pretty full. I'd say it's a good time to flip, if it's a stretchy strain it might be a little past time. Happy flowering!