I wonder if that is a scheme issue, Receivers or what? It might be something I alluded to in a video someone posted of his throws over 20 yards. He seems to get happy feet and lose his technique on some throws. As a side note, most successful deep ball throwers have a slightly more "over the top" throwing motion when going deep. He cant do his 3/4 motion and throw flat and be that successful deep.
I hope he sees this and works on it this offseason. If he can start hitting the deeper ball more successfully, whew, we will be tough to stop.