Nute question..Transition from veg to flower

I am looking for advice on when I should start using my flowering nutes. I am using MOAB and Flora bloom and kool bloom for my babies. I have heard that it is best to start using these sort of products slightly before switching to 12hr photoperiod. Any Input would be helpful.
Thanks

ive always done the switch right when i changed them into flowering and never saw the slightesy problem pants have always shown sex in less than 3 days so maybe it helps

use flowering nutes right away...

i use flowering nutes for every stage of growth so i know you'll be fine.