When, When, When am i supposed to start Flowering?

Hey yall. I had a horrible nute burn accident before with my DWC setup but my girls seem to of recoverd well (all the leaves that burned up fell off and new one popped out).

So now I am back on track and Im not sure when do i flower. They are all about 8 inches tall and have been vegging for 7 weeks and I think its time.Pleas let me know how i tell. oh the strains are Nirvanas Northern Lights and Fem Snow Whites.

Thanks

hey sgoldenone, this is my first post here and i'm on my first grow but i have decided to start flowering. i have 2 plants from nirvana's northen lights seeds. one is 8 inches tall and the other 12 and i think they have been vegging for a month (havn't been paying attention as i never though they would grow due to my crap set up) i canged the timer to 12/12 yesterday and will tell you if i get any good results if you can wait about a month!