switch now mate, it's time! ...grow nutes will mess with bud development...
You say switch now but I am only at day 31 surely that's to early to switch, I know you have more expiereance then me and I bow to your knowledge but 31 days just seems to early to me. If I was to switch on day 32 how long would it then be before I would be looking at harvesting certainly not in august like it would have been, your advice has left perplexed and unsure as to what to do......
... these plants are on a clock mate, you cannot alter their course significantly at this point... if you want, try a week of grow-bloom 50/50 blend, but to my eyes, these girls are done with stretching, it's bud building time.. they will still grow a bit more too during this stage,...

-- no genius here mate! Everybody starts with Auto 101, right? And make no mistake, auto's are more tricky than photo's on several levels,... nothing beats sheer experience too, to learn and read the plants, manage pH'ing in solutions and grow media,... research is as much about learning what NOT to do!
--keep grinding mate, you'll be cranking out phat buds soon enough! 