Planted big boy tomatoes grown from seed indoors. Transplanted and they grew to Huge plants, few tomatoes, but the ones that are ripening all have a hard whitish layer all around the tomato just under the skin. The center of the tomato seems normal. Had this same problem last year. What am I doing wrong. I water thoroughly twice a week or oftener if temps get too high. This year I put grass clipping mulch around each plant..... Help