also you dont neccessarily have to wait to change to your flower formula, i would just make sure the ppms are the same when u switch, the plant in theory should flower better if you change the nutes when u change the light cycle. But at the same time it takes time for the plant to switch to flowering however the flowering nutes should help it convert better i would think. If your plant is starting to flower and you have flowering nutes i would think of it as a catalyst. If you are starting to flower and still using veg nutes, i would think it would retard the plant.