You've done something horrible to your skies. I don't know what you did, but here look:

Left: Major major posterization occurring, with single bands of grays 10-20 pixels wide. This has been stretched in post processing beyond recognition, and you probably did it in 8 bit mode too.
Right: This is what happens when I slide levels all the way to the left. Your entire huge sections of sky are all just the exact same value of black. Why? Are you trying to make it look like infrared or something?
In general, the skies just look goofy, like you went over them 200 times with a huge blur brush or something. They don't even look like they are from the same scene (is that what it is? Did you try to green screen in a more interesting sky?) Plus, when you make them that high contrast, the clouds become very distracting. Like in #3 especially, that one random cloud draws all my attention, yet it is probably the least interesting thing in the scene. You don't want to be drawing attention to the least interesting thing in the scene.
Also, what is going on here:

Major posterization again, and weird halos, as if you massively oversharpened? Or perhaps tried to go around this tree with a hand selection tool? I'm not sure, but it didn't work, whatever it was. This looks very photoshopped.
Go back to the originals and:
1) Don't butcher your skies. Just leave them alone however they were.
2) Go easy on the contrast overall. As in, move the curves to wherever you think they look good, and then do 1/4 of that.
3) If you're going to do lots of lighting edits, make sure you're working in 16 bit mode, so you don't get posterization.
4) Don't ever use a blur brush or gaussian blur filters unless you really know it's the right thing to do, unlike here.
5) Don't do whatever you did to make those halos (hand selection, etc.). Whatever it was, it looked like something you did to mess with the skies, which you shouldn't do anyway (see #1), so that might resolve itself.