Technical Issues

I am not a pro in the photography but I still believe that the first photo is far better than the other two and has the main object in focus and captures it in detail therefore it doesn't matter whether the sky looks blurry or not. I think you should try to submit the first photo again.

in addition to what @madscica commented on, if you view at 300% you can see artifacts between the sky and the other objects.

For the first photo, it isn't sharp, and it has noise (check the sky at 100%). Also, the highlights in the bird are blown, and there is vignetting in the corners. Composition would be better if the bird were not so close to center.

For the second photo, again, not sharp, noise, blown highlights, and vignetting. It would also be better if the fence were level.

For the third photo, it could be sharper, and there is still noise in the sky and blown highlights (but not as bad as the others). The sign should be vertical and the wires in the botthm left should be removed, as should the tiny logo on the sign (it almost looks like a dirt spot, but it is actually a logo or something). You used a smaller aperture so the vignetting is gone, but now I see a spot in the sky from dust on your sensor.

It might be helpful for your to Google "rule of thirds" to improve you ccomposition a bit. Remember when shooting for stock to leave room for test, many buyers will add text when they use the photo, and if they don't need the extra space, they  can criop it themselves.