At small sizes, those images look absolutely lovely. Nice colors, nice composition, etc.
However, when viewed at full, 100% zoom, there are some serious issues. They look fairly compressed and "jpeg-y" and either you or your camera is applying some oversharpening. Observe the edges here in your first photo:
Notice that white outline outside the rock and dark outline inside? Oversharpened.
And, while we're looking at it up close, look at the sky. It's kinda blocky. That part isn't the most egregious area, but you can still see it. Either you are saving your images at too small a size/too compressed or your camera is.
On that second picture, did you replace the sky? Something about it looks really weird besides the oversharpening issues.
There also seems to be an odd frame and drop shadow on the images.