When to switch from veg outside

Ok let me begin im a first time weed grower. Im growing outside in the uk using flora grow feed soooo i started me seeds off in the first week of may so they are about 7 or 8 weeks old so i know that the plants will do its thing with day light hours but when do i start to bring down the grow and up the bloom as im not sure the guide i have is for out side growing and is for lights

Any help much appreciated

About 2 weeks after your daylight hours are 12 hours or less. But start cutting back on the "Grow" portion of your feed a couple of weeks before. Nitrogen is easy to replace if it shows deficiency

Thank you for your help

Your plants will start flowering when the daylight hours have reached around 14 or less hours of daylight. 12/12 is for indoor only and does not apply to outdoor growing.
For my area the stretch happens around the first week of aug. So the last week of July I switch to a flower nutrient line.
Hope that helps.

This really dose help thanks