I use molasses throughout the entire flowering cycle as well as the veg, if they need a growth spurt. Molasses encourages the plant to use all the stored nutrients to maximize growth. So using molasses will grow faster, but you have to watch for defeciencies, if you dont continuously fert .. half strength flowering nutes, with 2 tblspn/ 5 gallon at every feed... use molasses during flush to cut flush time in half ..
vinegar is fine for lowering ph, but if in a resevoir or jug is sitting for a few days, check ph again, because vinegar isnt stable enough to maintain ph for more than a few days