You are getting some significant stretch on your smaller plants. This tells us that you either do not have enough light or your light is too far away or both. First of all, don't start any more seeds. As you can see it can be problematic when you have a bunch of seeds started at different times. Second, you need to do something to raise the smaller plants up so that you have an even canopy--set them on milk crates, boxes, something like that. Otherwise the 2 larger plants will continue to get larger and the smaller ones will be spindly with very few bud sites. Next, get your lights right down within a couple of inches of the top of the plants, which now should have a nice even canopy. You need some kind of oscillating fan in there to move the air around and help strengthen the stems. Tell us about the lights you are using--size, type, wattage, lumens (if you know).
I'm going to talk about genetics a bit. If you used seed you got out of a good bag of weed, chances are that the seeds are a result of selfing. These seeds were created by the female sprouting male parts. This makes the hermy gene dominant and hermies beget hermies. If you end up with all females this is almost certainly the case.
Before you start building a flowering box, you need to know what you are going to need out of a flowering box. You need to figure out how many plants you want to grow and how much you can afford--you will need to step up your lighting, you will need a good ventilation system and misc other things. I can absolutely guarantee you that you are going to need way way more light than you have now. Flowering requires a minimum of 5000 lumens per sq ft. This much light creates some heat.
You cannot put plants outdoors until all danger of frost has passed--frost will indeed hurt them. What are you feeding them?