Yup, I see you having no problem getting at least 1-2 ounces off 3 plants. You will definitely need to LST those girls. You don't need to top either. If you bend each girl over flat you can have each one take up an equal sizes rectangle of space in the box. Then as the arms start to reach up towards the light pull them down and keep it even. It should take about 10 minutes on each plant every 2 days or so. What are the dimensions in your box? If you can figure out some way to get more vertical height it will make things a lot easier. After you transplant to bigger pots things will get tight. Your box is cardboard right? Can you find another box of the same size and secure them together with tape? Then you can cut a door into your box and you will have plenty of room. A good guide, that I go by, for using the right sized pot is to have the pot take up 1/3 of your grow space. That should provide plenty of room for your girls and their roots.