His freshman year he threw much more over the top and now his release is almost a side-arm. This type of change is often associated with elbow or shoulder injuries and may explain some of his throwing issues (hitting receivers in the feet, throws blocked at the line of scrimmage).
It may be nothing-and he has changed the throwing motion for other reasons, but I believe there is a high probability that there is a lingering injury issue that has had a large impact on his velocity, range and accuracy.