Think that is an over nuting problem. It looks like it's smaller than the other plant so cut back a little bit on feeding it nutes and than go with more nutes. Just flush them the next time you water and you should be fine. The other plant looks goregous though.

16/6 light is fine. I would wait a few days to flower and give them 24 hours of dark and go 12/12 until you're ready to harvest.

Good luck =D