The damage leaves is insect damage., mostly from thrips or leaf miners. The damage occurred when the leaves were new and tender, before the leaves matured. That type of damage is actually very common. Although the leaves are curled they are still producing energy for the tree. In the future you can avoid the damage by spraying the new leaves with a horticultural oil, or even with a water spray a couple times a day until the leaves firm up. Or you can just do nothing.