I'd wait before freaking out. A+ to AA is supposed to be the most difficult jump and he did miss a lot of time before coming back last year. Let's see what his stuff looks like in August.
Fort Myers to Chattanooga is also a transition from an extreme pitchers' park to an extreme hitters' park. Combined with the level change, that is fairly tough for a pitcher. Even if they pitch well their numbers won't be as pretty, given the environment.