content: It's possible that the smaller plants were planted slightly later (maybe he's got a rotation going). I would guess that's what's up, just by the fact that there seems to be a fairly clear divide between the smaller plants and larger ones. And they look fairly healthy to me, as far as I can see from the picture, which is not much. It's not like you can really tell if there are nutrient deficiencies, or other issues from this shot. I can see what looks like a bit of yellow colouration on some plants, but that could just be because the crop is nearing harvest time. I think they'll make out just fine.