Grey spots on your image are commonly caused by dust on your camera's sensor on DSLR, Mirrorlesss and even compact cameras.
You can test for dust by closing your aperture (A) down to f/11 and taking a photo of white clouds. The small aperture will ensure the sensor is in focus, and will show as little grey smudges.
We have handy cleaning kits if you would like to clean your camera sensor yourself, or we can do it for you.
Sensor Cleaning is $89.99