PPM for Vegetation and Mothers

Growing in Rock-wool. Due to my flower room not being ready, I have had to keep my plants in vegetation for 2 1/2 months. Should I still keep my ppm at 800 on the high end since they are still in vegetation, or should I raise the ppm since they are bigger? Where should I be? Also, I am using RO water, so if the ppm is too high, then to bring the ppm down all I need to do is simply dilute the feeding water with more RO water to get the desired ppm, correct. What should the ppm be at for feeding my mothers?