I think that most trees in cool regions get the majority of their good photo-synthesizing done in the first few months of leaf growth. Leaves are constantly being attacked by insects and pathogens, and I'm sure that the methods that the tree uses to retain them (harden them, add more harsh chemicals to them, etc) interfere with the straightforward process of turning sunlight into food. I imagine that most northern trees can survive just fine if they get 3 or 4 good months of good photo-synthesis in with nice juicy green absorbent leaves, and if they are just dropping their leaves now, in early August, that means they had April, May, June, and July to make food. I think trouble is more guaranteed when you get several adverse events several years in a row. (Drought one year, insect infestation another, very late frost one year, very early frost another, too much rain another). I think the East has gone from one or two years or rather severe droughts to a summer with too much rain in many places. The trees might be reacting to yet another stress. I wouldn't write them off until you've had one or two "normal" years, to see how they do when conditions are actually favorable for a switch.