I have five exterior fans only front porch that were installed a year ago. All were brute white when installed. Now three of the five motor units and blade brackets have turned a light tan color. Also some of the pull chains have changed. This can be two fans that are 10 feet apart. Have you had any problems like this? Appears some may be from different lot with defective paint?

It's not defective paint, it's cheap paint.

Sad to say, but these fans are more often than not, junk. Disposable. Like many things in our lives these days.

Sorry I can't add anything constructive.