It's a depth of field issue. The blurred areas are all along the bottom part of the image, not just in the bottom corners. The background's sharp, so my guess is you focused on the background and didn't close the lens down.
The Fuji 617 lenses are basically 8x10 lenses. Such lenses need to be stopped down all the way to give full depth of field, and hyperfocal focusing distance must be used. If you didn't do this, then it's no surprise you have out of focus areas. These are VERY sharp lenses, but you need to use superb technique to get the most out of them. 617 photography is definitely not point and shoot!
In fact, focus can be such a problem with near-far scenes that I used the groundglass focusing screen with mine. It works fantastic. The only thing is you have to shoot a full roll for each new composition. But that's not much of a problem when you can take only 4 shots per roll. I just bracketed: 1 exposure right on, 1 low and 1 high, finally one more right on for insurance, and voila, roll's done with !
As a general rule, I blame myself or my technique before I blame my equipment. Most of the time the problem is caused by me rather than by the camera.