I don't really know if 30 min at 4.0 would do anything or not I do agree that you should mix your nutes up seperately always and adjust ph before you add it to the plants. Another thing would be big and sudden changes in water temp (more than 15 degrees difference or so) would be pretty stressful for your plants and may cause damage to the roots but I''m having trouble with heat causing lockout. I still think the problem goes back to fert buildup, just based on the issues I've had with it myself.

Hey cm, can you post some new pics? And if you can get a pic of the entire setup at once in some way, that would be great as well.......hps lighting off!!!!