When to switch from preflower nutrients to flower?

I have settled into a routine with all my autos (and they're all I grow) of starting their nutes off about week 2 or 3 with 1/4 strength grow AND bloom nutes... and increase the doses to 1/2 the next week if they're tolerating them... and so on. With MY nute line, I never get to full strength grow nutes as I find it too strong for my plants... but the bloom nutes are well tolerated and I think it's a good idea to "tell" the plant I'm here to help it... So MY routine is not when to ADD bloom nutes but when to STOP grow nutes - and that occurs about week 4-5. Autos don't like a whole lot of nitrogen in flowering stage and too much nitrogen can lockout calcium which is critical to the flowers... so, since they're already in flower, I would recommend dropping your FloraGro back by half at least and doubling your FloraBloom... Generally, if you're not as weird as I guess I am about things, you should start introducing bloom nutes when the plants go into pre-flower... it just encourages the formation of the buds and gives the plant the calcium and phosphorus needed - and only use calmag IF the plant asks for it (shows either calcium or magnesium deficiency) and then only once a week. Good luck with your grow - it looks really, really good!