It's very good that you put more lights after switching to 12/12.
What you are asking is quite a floozy of a question, because no one really knows what to do or when to optimally change the nute pattern.
Before, I used to make a mix of the 2 nutes. In the first week of flowering I kept lowering the veg nutes from 100% to 50% and in the next week to 0%, always compensating with flowering nutes.
Now I use flowering nutes that have a very nice N-K-P, enough N to not starve her in the 2 first weeks of flowering when she's not used to it and pretty much K and P to really get that bud production rolling.