I have no idea what's been going on, but this happens like clockwork around week 6.
In 12/12 Under 1000w hps (20" from light)
Nutes: GH floraduo 4ml/gal A, 8ml/gal B
Total ppm: 720 (.7)
Ph: adjusted to 6.0
Temps: 75 hi, 60 lo
Humidity: very dry (which might be the issue)
I used to add cal mag...