Merry Christmas all! II am growing aeroponically using Mills nutes feeding on the light side due to new clones have only been in box for 7 days. They were in perfect health. Air temp averaging 73, water temp averaging 68. Humidity around 40%, ph 5.8, ppm's around 600. Top leaves start to lighten, then turn a reddish brown and then they curl up & die all within a 48 time frame. I am growing under a 315W CMH bulb which is positioned 3 1/2 feet above the tops of plants. It is not light burn causing this. Any opinions from aeroponic growers that may have seen this before?