I think there might be too much info on the net.LOL sounds crazy but i have researched and these are all the possible problems.

Nute Deficiency
Nute Burn
Over Watering
Ph to high
Ph to low
Plant did not have enough room to root properly
Nitrogen Deficiency
Too much Light
Not enough light
Burns from hotspots.
privatepile Reviewed by privatepile on . Yellowing Leaves(I have researched) Ok i have a problem with my plants.The bottom leaves have started turning yellow. I have Top Soil(no ferts).The strain is White Widow.They are under 3 x 40watt daylight CFLs,They are a few inches from the plant. There is a fan blowing on them. To water i use bottled water so the PH should be fine. I have researched a lot and i think most of the time its nute burn. Rating: 5