Drew, what you might need is a calibrated monitor. The picture may look different on their screen than it does on yours.

Ever go into a TV store and look at 20 or 30 screens, all showing the same image, but with a wide variety of saturation and brightness etc? They're all SUPPOSED to show the exact same image, but they don't. The same thing is true of monitors.

Most monitors are way too bright at the default settings. If you haven't messed with yours, the image could look fine on your screen, but be dark (and thus appear under-exposed) on the reviewers screen.

Using your histogram when you shoot might help avoid this issue. Then again, if you're happy with the photos, that's all that matter, so screw 'em!