Check for dust on the lens. Dust on the lens will be visible at different focal lengths but in different places and different densities. Or there was a heck of alot of crap floating around in the air. I would shoot a few more sky shots after cleaning the lens. If they are still there, there may be dust inside the camera. If that is the case you have to take it in to be cleaned. Onslow, Hot Pixals will be in the same place all the time everytime no matter the settings. Hot pixal means that the specific pixal is toast and will always show as white or red, unles the camera tries to map them out. However if it tries to map it out it is usually the color of the surrounding pixals which is where the camera grabs data to fill the hole.