Here is a little trick you can try to see if it is your image or not.
Open the image in gimp. duplicate the layer several times, so you have several layers of the same thing, one on top of the other. I have found that when you do this, if your image has stray pixels, that will make them show better. (obviously you wont save the image that way, but it will show you any flaws)
It's best if you have a background layer that is magic pink or a really intense color, the stray pixels show up better against that.