sunscald.

Dax

from my web search, sunscald seems to be more of a fruit or trunk issue than leaves. Leaf scorch appears to result in browning of the tips, not whitening of the central region. The leaves look healthy otherwise (although some do have some brown spots, and the area in the central vein is the most protected from the sun, as the leaves are somewhat curled as well.

Just came upon this while seeking similar explanations on a small orchard I'm rehabilitating. Herbicide use appears to be a key factor in bleaching of this nature. UC Davis IPM sites and a NC State University site both indicated that carotenoid pigments can evidence nearby or direct use of Clomazome or other synthetic herbicides that damage a number of plant species.

Hope this is, at least, an answer if not an aid at this late stage.