1 Grow Room with Plants at different stages

Hey RIU. I'm doin my first hempy grow, HPS and MH 400watt. I had been having problems getting seeds started in rockwool and ended up wasting many of the femenized seeds i had purchased(Northern lights). Figured it out with 3 seeds from some this seasons outdoor crop that got pollinated and then decided to do the last of my fem. seeds, having figured out the rockwool issues. The 3 initial seeds are much farther along in veg and i could probably switch em over to flower in the next 2-3 weeks. The fem. seeds appear to have just hit the reservoir and are significantly smaller. This is all in a grow tent, and I don't have room to have 2 (flower tent/veg tent). I'm trying to figure out a way to allow the Northern Lights to veg out a decent amount while starting to flower the others so they end up about the same size. The only idea i have now is to keep the lights on 18/6 but move the 3 larger plants into my dark closet or something after 12 hours of light every day. Obviously, this could have some problems. Just looking for some feedback though, or any ideas anyone might have!

If I were to do the closet idea, would I want to switch to the MH bulb and do the continued vegging of the NL plants with that?

Also, I realize everyone says to definitely do this, but I don't have a fan blowing on my plants because I haven't had a chance to go pick one up. How serious of an issue will this be down the road if I continue with simply bending/blowing around the stems every day to encourage stem strength?

Thanks a lot, and sorry for the lengthy post!

Japhy