From the looks of it... You have already let them get WAY too tall for that grow box.. Especially if you havnt flipped them to 12/12 yet... I would say now would be a good time to take some clones.. and flip them asap! You may even want to consider taking your clones from the top of your plant.. and then cutting it roughly in half... Look up "Topping" on youtube... you will NEED to do this if you want to keep them short! Those plants will grow about 3x their size once you flip to 12/12.... They look healthy tho! Take some cuttings and let the flowering begin!