Noooooo....! After it finishes blooming, you may want to trim it, but take your cuttings above the "Y." Are there five plants in one pot? It's going to get pretty crowded in there. After the blooming is over, if there are five plants in one pot, you might think about separating them into their own individual pots. Maybe in early spring, at the latest.
I'm duly impressed that they are already so large and healthy grown from seeds.
Now with all that said, you're the mama and you know best. Don't cut them back if you don't want, but if you wake up one morning with something pinning your arms down that smells like baby powder, well we told you so.
