Yup... If your plants are already in 12/12 save the Grow Big for the next veg round imho... They'll don't need the N now that they are starting to flower... Just use the Tiger Bloom and Big Bloom and the solubles - Open Sesame, Beastie Bloomz, & Cha Ching according to what week of flowering you're in... You can go to Foxfarm.com and download the hydro or soil feed chart... imho use 1/3 to 1/2 strength feedings and slowly increase if you don't see any nute burn on new growth.
According to the Fox Farm schedule, during weeks 3 and 4, you're supposed to feed them Tiger Bloom, Big Bloom, Beastie Bloomz, and Grow Big.
hXXp://foxfarmfertilizer.com/soilfeed.pdf
Copy and paste the URL (link) above into your browser. Change the "XX" in "hXXp" to "tt" to make "http". We're not allowed to post direct links to other sites. You'll see the Fox Farm feeding schedule for soil. You are using soil, right?