AIUI, it wasn't the limited diet, but the lack of fresh food. What I heard was that basically everything you eat has vitamin C in it (which is why our bodies forgot how to manufacture it on their own -- why bother making your own when it's already all around you?), but that it decays fairly rapidly. So it doesn't matter how diverse your food supply is, if it's all canned / salted / preserved, you're going to have problems.
I guess it depends on how "routine" OP's routine is. If they're eating just potatoes and bacon every meal, they're going to have problems. But if they have 2-3 forms of starch, 2-3 types of vegetables, and 2-3 forms of protein mixed together, I think they're probably doing about as well as most human beings have done throughout time.
That said, never hurts to take a good multivitamin. :-)