Julie,
Welcome! You probably should know that you shouldn't sharpen or over sharpen images for upload. And I think that what we are seeing may be that. Unless you are shooting, ALL the time at high ISO's, you're probably sharpening the image and then uploading it.
I would also suggest that you shoot your images in RAW and then in Adobe Camera RAW, sharpen there slightly and then skip sharpening later,since the printer will sharpen to size, if your image is sold,
Nice stuff, just watch that over editing,
Rich
Do you know the Noloboffs?