In my case - I'm in Soil 2nd week of veg, 600 watt MH, 7 liter pots, Temps are between 65-80 Humidity 35-45%, Only have exhaust fan and an oscillating, 10 sq foot closet, Don't know PH or PPM. Haven't started w/ Nutes yet.
Only one of the plants is doing this, all the others are fine. I haven't watered in about a week because the soil is still moist.. Moisture light isn't going off either.