This is my theory: fungicides are to blame. Even if you personally don't spray, the volume of fungicides being used is so great it spreads through wind and water. The fungicides are killing the mycorrhizae fungi that helps plants get through droughts.
We recently went up the gorge, something we haven't done in a few years since the fire devastated the area. I was shock and heart broken to see Oneonta Gorge defoliated. It is lifeless, and off bounds.