MycoDananswered grow question 3 years ago If you're using the GH 3 part I recommend doing a full water change right before switching to flower. Also 400ppm's sounds low to me. I'm usually around the 1200-1500ppm range in bloom, but I follow the Lucas Formula which only uses the Micro and Bloom nutes in a 2:1 ratio micro to bloom. Are you using any supplements or just the GH 3 part base nutes? What kind of water are you using?