Why is my tomato plant wilting and dying?

[brian1269]

I can't figure out why this is happening to my Rutgers tomato plant. It's in an earthbox and was doing great until about a week or so ago when it just started to wilt and stop setting fruit. Not all the leaves/branches are wilting, just the majority, and the same plant on the other side of the box seems to be in a lot better shape. It's getting good water, I don't see any type of pest problem, and don't really see any bad spotting on the leaves either. Help.