Me and a buddy fished up there last fall and saw the same thing. It is my understanding that shad are very weak when it comes to the temp changes. Last fall when we were there it was a sudden drop. I'd guess that the warm days and cool nights are too much for them.
The really crappy thing was we couldn't catch a dang thing! There were shad EVERYWHERE. Why would a bass eat a lure when they had all that food everywhere?
