the plant needs more than just Nitrogen, Mag, Cal and Iron. If you dont have a ppm meter there is no sense talking about ppm. I take it this pure Grow you are using is a stand alone product?? I ask this since I use GH 3-part which consists of 3 sep bottles (Micro, Grow and Bloom), and during grow each has a certain amount I use. I cant say add more or less since I dont know anything bout the nutes you are using and dont want to steer you wrong. PH needs to be as close to 6.0 as you can get and what is the mix ratio of that stuff?? ml per gal?