Basically, the reason why people use veg nutes a week into flowering before they switch, is because you wanna give your plants that last good dose of nitrogen before flowering onsets. during flowering, you dont wanna give your plants any extra nitro at all, because it will slow down bud growth, and could potentially hurt your overall yield in the end. Personally, i would use the veg nutrients for one week into your 12/12 cycle, and then go straight to bloom nutes. Once plants start showing pistils, thats when your gonna want to use a nutrient thats high phosphorous, because that it the main nutrient that your nugs will want so that they thrive for you.
btw, are you using Tiger bloom with your Big Bloom?? i ask because Big bloom by itself is just a catalyst. It doesnt pack enough OOMF! for the plants to really benefit from it, other than the Big Bloom itself making the roots more able to absorb any other nutrients your giving it. Tiger bloom is the actual bloom nutrient that you should use if your only gonna go with one. But if you use Tiger Bloom WITH Big bloom, your plants will scream THANK YOU YOU FUCKIN GORGEOUS MOTHERFUCKER YOU!!! , lol. If you can pick some up man, pick it up, youll thank yourself for it later, n your buds will thank you for it too.
*** Edit ***Another thing that you could do also, is since Big Bloom is merely a Catalyst for anything else that you feed your plants, is use BB while your using Grow Big for that last week of flower. I use Big Bloom throughout the entire growth cycle, just to open up the roots a little bit more, and make them soak up the Grow Big even better, along with Molasses,and Super Plant Tonic. You can use Molasses throughout the grow also - alot of people prefer to use it only a couple times a week for its Macro-nutrient content, and some people even say it makes the buds sweeter, but thats not true. It does help a little bit with yield, but its also similar to using Big Bloom - in that it provides Macronutes to your roots, and opens them up to absorb anything else your giving them in conjunction with the Molasses.
--Sorry for the rant bro, but i just want you to have an option on what your doing, or at least have an idea of what your feeding them, or could be feeding them, if you can be bothered to pick up some extra stuff
