I go 24 7 for veg always, seems to bring them along a little quicker IMO, but some do say that after the first couple of weeks you should swhich to 18-6, and I get stuff like this at 30 day flower http://boards.cannabis.com/indoor-gr...coco-coir.html
Also, 6 weeks for flower is pretty short and most strains will take 8 to 10 weeks and some even take 12 to 16 weeks believe it or not.
Adieu