You know, low leaves in the shade naturally wither and die off. Your plants look quite healthy, although they are still showing symptoms that they are root-bound. If you've just transplanted, that should improve shortly.
Think about this! As your plants grow in height, you raise the light. The distance from the light to the soil surface and lowest growth increases, to the point where the lowest growth is now getting insufficient light to thrive, and will be sloughed off by the plant, after the plant uses up whatever nutes it can (=mobile nutrients), causing the yellowing and necrosis. I see you are still under shop lights, which are great, but remember their penetration is limited and it may be time to switch to a HID lamp, or just learn to live with low leaf shedding.
Do you have plans to flower in the near future?