Unusual yellow peanut color

I have recently seen several peanut fields or spots in the fields around the Tidewater AREC with yellow plants resembling nitrogen deficiency. Colleagues in North Carolina are also getting concerned with peanuts needing late season nitrogen applications. Similarly, in one of my research fields we noticed a part of the field with yellow plants resembling nitrogen deficiency next to dark green plants for the rest of the area. Indeed, early this summer Kelvin Wells, Extension Agent in Sussex county VA, brought in some samples of yellow peanut plants. Right away I identified nitrogen deficiency because there were no nodules on the roots and plants were starting blooming; also the farmer did not inoculate at planting. It was easy. But with the plants from my own field trial it is not so easy! Yellow and smaller plants had larger nodules than the bigger and greener plants and in a similar number on July 17 when I checked. Nodules from both plants, green and yellow, were dark red when cut, indicating active nitrogen fixation (pictures are attached here Unusual peanut color). The green plants were planted on May 10 and the yellow ones on May 22. I really do not have any other explanation than probable negative effect of high temperatures and dry conditions experienced by late planted peanuts in Virginia this year. This could have affected root growth and nodulation for young seedlings and carried nutritional imbalances over to later stages.