In addition to what the other people said, you should also move your intake fan to the bottom of the grow cabinet, and get rid of the foil... Just paint the inside white.
It's much more reflective than foil.

Good luck with your widows, I vegged my last WW for about 2 weeks, and switched to 12/12 at that time... The plant was about 5 inches tall (not sure what that is in cm)...
By the time I harvested her, she was 2 feet tall...