First step that I would do is clean the glass on the scanner. Most scanners have the Full paper glass, where you place the paper, and if you are using the feeder, you'll see a second thin glass (normally about an inch wide). Clean this as well.
A software cloth should do the trick. The glass could just be dirty. I have seen this before. If its still coming out blotchy when Scan to print, It might be the scanner itself.