I got 12 plants under 3- 4ft 8 tube t5s, they're 5 weeks old and using techna flora grow, magcal and sugar daddy, stared 1/4 strength slowly worked up to 500ppm so far at 6.5 ph, the white you see is not powdery mildew it is diatomaceous earth used to kill a small infestation of fungus knats...