yellowing of newer leaves from base?

[kevinrs]

I am posting this separate from the insect problems I've posted, since at 8 miles away, the soil and everything's completely different, including the problem.

This plant is the worst, but I'm seeing signs of it on 8 plants, There are some spots turning brown in the middle of the worst of the yellow leaves, but not on most.

What looks like yellowing on the undersides of larger leaves and stems, I think is just light reflecting off the ground.

Could it be a deficiency? or is it a disease? I'm not seeing anything quite like it so far searching.