Quote Originally Posted by JackdaWack
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.

It's not just the PPM but more of the percent of the total NPK balance that you need to know. The PPM is only accurate at the time you balance your NPK anyway. After the first hour it will start to change as the plants uses up some nutrients and deposits back others it does not need at the cycle.