You're doing everything right. I've had a few that were like that; can you check your roots? The buffers in the nutrients should be able to control the swing. You can run the gambit and start checking the separate run off from each plant. That's what I do first when this happens to me. There could be some slim somewhere in the grow medium for example. You're not using rock wool are you? The only time I had that problem was when there was one plant that had slim on the roots around the ball so the long roots did not show. The only other time was when I was still using rock wool.
Zandor Reviewed by Zandor on . HPS Lights adjusting Ph???? We replaced our lights from a T5 to HPS and we've had major alterations with our ph and ppm. With the T5 the ph and ppm remained consistant. We would go for days with the same ph and the ppm alternating at the 1320-1290 range throughout the day. Since the exchange of light to HPS, we are adjusting ph two to three times a day to lower it to the 5.2-6 level. Our water is being absorbed more rapidly due to the heat. Because these issues didn't exist before, we are pretty sure it is the light Rating: 5