I don't see anything that suggests that the sensor needs cleaning, but it's your camera, so you should know.
I like #'s 2 and 3 better than the first shot because the colors seem more correct to me. #1 has colors that look fake or un-natural.
#2 looks like you may be boosting the contrast to get a more dramatic sky. If so, then I would say it's a bit overdone.
In regard to colors, there are different techniques that you can use to be more certain that your colors are correct, such as the use of a Custom White Balance using a Gray card. For the utmost accuracy, you would have to include a gray card in the scene (say in a corner, so that you can crop it out with a minimum loss of image) and shoot in RAW mode. Then in RAW processing the tool can be used on the image of the gray card to correctly set the color temperature.