How can I tell if my babies are in pre flower? Is ...

preflower starts at the lower to mid nodes, little white hairs/pistils, then developing a calyx if its female. your plant does not look to be in preflower yet based off of that picture. If its an auto it will switch around week 5, if it photoperiod plant 12/12 lights will set it in flower. calyx can sometimes be mistaken for balls as they are both bulbous. Balls have a small shaft/stem and tend to hang downwards ever so slightly vs calyx do not, and calyx has one or two hairs/pistils coming out of them best of luck

It does not look like that plant is in preflower, you would notice bud sites (white pistils) at the growth tips and possibly individually at the nodes to a lesser extent. If it is an auto you are growing (not clear from your journal) there is not much you can do besides trying to keep it as healthy and fast growing as possible. If the strain flowers based on photoperiod (eg. 12/12 light cycle) then maintain vegetative light cycle (18/6) as long as possible to grow it to a large heathy size before inducing flowering. This can repair a lot of early mistakes. Just keep in mind a plant can double in height from the point flowering begins. Happy growing! 👍🌱