Love the bottom half; top - not so much. Maybe B&W for this one?
Not sure what you sky originally looked like but those who pulled you up on it are right.
Even just a normal cloudy day; the way the camera captures the colours in the sky looks wrong to us. Normally the problem is the sections of thin colour contain a lot more cyan than the blue tones we are used to, and it's that colour in yours that catches my eye. An easy fix is PS is to mask other areas and use a Hue/Saturation layer to modify only the Cyan's towards more natural blues. Might not seem like much but I've seen some shots where it makes a world of difference to the final image.