Hi, I'm trying to diagnose a leaf disease I am seeing on my sugar maple tree. I had an arborist out and he ruled out everything he knew of the typically impacts maples and said to wait and see if the problem comes back next year. He cut a branch and there was no streaking in the bark so he ruled out verticillium. This is a large, mature sugar maple tree. Mid-summer we had some dead leaves drop from the tree and thought it was a little strange. Now we are seeing that a part of many of the leaves are dying, often along the vein. The whole tree is impacted, not just one side. It's fairly evenly spread out amongst the branches. I've attached some pictures. Please let me know if you have any thoughts on what it could be and if there is anything we should be doing to treat the tree.