Quick follow-up: Came home on Friday and the entire plant was wilted. Went ahead and pulled it out to be safe. Really wasn't producing well anyway, it was the biggest plant I had but only 3 big tomatoes on it, that had just started to blush. Guess I'm probably safe to eat them.

If besides wilting, the leaves all turned dark or dried out so quickly, you probably have Late Blight. Lots of info and pictures here:
http://www.longislandhort.cornell.edu/vegpath/photos/lateblight_tomato.htm

If so, follow the directions at the site about bagging the damage. If you see similar damage on the other plants, remove the damaged areas immediately.

If that doesn't seem to be the problem, you can use these diagnostics:
http://vegetablemdonline.ppath.cornell.edu/DiagnosticKeys/TomLeaf/TomLeafKey.html
http://aggie-horticulture.tamu.edu/publications/tomatoproblemsolver/

Interesting - no late blight reported anywhere near Colorado. Also I didn't see any damage on the stems, only the leaves. According to those websites, it actually looked more like drought stress, though it only hit that one plant and completely wilted it while the others are still fine. Who knows. That plant was the biggest yet least productive of the four anyway.