I have 3 plants in peat cups like the photo and they are under a T5 light. The light is sitting on 2x4’s so the spacing is 5-6â€. I’ve noticed that the bottom leaves are turning a light green, or yellowish green. The leaves are at about the cup diameter now. My question is; is the yellowing of the lower leaves normal, or is this a sign of a problem? And of course what is it and how do you correct it?