Almost certainly you are seeing the effects of oak leaf blister, a common fungal disease. The fungus attacks the new growth when it emerges in the spring, causing puckering and distortion of the leaves along with some spotting. Some of the heavily infected leaves drop from the tree during the spring, while many of the leaves remain on the tree. Although the spotting is unattractive, the disease is generally not life threatening to the tree and treatment is generally not recommended.