Newb question on flowering!!!

i am going to start the flowering process on the 13th of this month when my 3 babies are about a month and a week old.. so my question is what exactly do i need to do start the flowering stage? besides the obvious of 12/12 !! do i need to feed them? or can i honestly just change the lights to 12/12 .....

theres pics in this thread of my plants:
https://www.rollitup.org/indoor-growing/309931-one-month-veg-closet-grow.html

Well I like to use veg nutes in the 1st week of flowering and then on week 2 use half veg and half flower nutes then week 3 just flower nutes.
What are you using for nutes?
What lights you have? cfl's or hid?

12/12 will cause the plants to flower (as long as their not auto-flowering). It is a good idea to use veg nutes for the first week because it usually takes about a week of 12/12 for the plant to fully start flowering.

ok so i have the dyna-gro for veg state, but never used it at all, cause i have FFOF and never needed to feed them, except of course water ... fo rthe flower stage i got tiger bloom.. do i absolutly have to use nutes or can i just water?? oh and to answer your question hardroc, i am using a 400 watt hps light ....