What do the bottoms of those affected leaves look like? Maybe you could pluck off a couple and take good close-up pics, of the top and bottom and post. Is the damage on the top or bottom, or both, or interior of the leaf? Are there any tiny little critters hiding on the bottoms of the leaves? Do the leaves come out/emerge with those patches or do they develop later?
Haven't seen anything that looks like that on my elm.