Our Velvac chrome-plated outside mirrors had become covered with what looked like water spots or something similar. I tried everything I could think of to remove them, including wax, WD-40, several cleaners, etc., but nothing worked.
After looking at the mirrors for a while, I noticed that it almost looked like the surface had tarnished, so I tried a Blitz silver cleaning cloth my wife bought to clear her silver jewelry (available from Amazon, and many other locations for a few dollars). First, I wet the chrome cover with a wet paper towel and then rubbed (vigorously) with the cleaning cloth and WOW - the chrome cleaned up like new!
I was really surprised how well this worked -- if you have discoloration of chrome finishes, you might give it a try.