These are the pedals...
https://www.nashbar.com/bikes/Product...2_10000_200435

Recently, I noticed that my drive side pedal was a little off.

There's a small gap on the underside of the pedal, which I showed in the picture with the red lines. The gap should be even throughout, but there's a bigger gap on the outside.

I've tested the pedal and I've actually ridden maybe a hundred or two miles on it like that, and I haven't noticed anything different about the pedal.

Any ideas how to fix it, or what the problem might be?

Don't know those particular pedals, but it looks like something is broken on the outboard side. Can you click in properly, or does it feel different since it started looking like this? If the outboard side broke, it's likely the inboard side will eventually break also. "Eventually" could be days, or years. If you can disassemble them, you should see something broken (you may or may not be able to fix it). If you can't disassemble them, then it might be wise to get new pedals.

Yeah, it looks like a hinge pin broke on the cleat clamp/holder. I have the same pedals and so far no problems but I can say that that ain't right. As long as the other side holds your ok, but when it goes it will just flop apart. You can take the upper chrome plate off the pedal and have a look in there to see specifically whats broken, If memory serves its held on by some phillips head screws (I rarely look at my pedals and its been 9 months since I had them apart for some silicone spray at those pivot points).

then again, new one's, 40 with a 20% discount....