While it may be a little bit of "all of the above," I think the biggest issue is that the playcalling has been predictable. Fitz is getting handoffs on a limited number of plays, and almost always on 1st down. Give him some space to run, and I think he's doing fine.
"He makes it really easy on you as a coach because he has tremendous football instincts," Michigan tight ends coach Jay Harbaugh said. "Things come really naturally to him. He doesn't have to see things too many times. He has a good sense for how things should look and feel, and he's a tough, physical guy."