I know this comment is very late, but still, base on the photos, the problem is oak mildew. It is caused by fungus Erysiphe alphitoides. It infects younger leaves and soft shoots. In fact, its severity varies according to the weather conditions in a particular year, and it is worst during warm and wet summers when humidity is high. Also, some leaves may shrivel and blacken. However, this kind of tree disease can't kill a tree but it can weaken it and can lead to an oak decline. You can also check Tall Timbers Tree Services' blog section to guide you make in maintaining your tree's health.