I've been concerned about my red wag platy as well... I have two of them. One is a very beautiful red / orange color, and the other is a really pale orange... I always thought it was unhealthy but it doesn't seem to be that way. They have quickly become my favorite fish because everytime I get near the tank, they come to the edge and follow me around to see what I'm up to.
Unfortunately the pretty red one seems to have some weird bald spot on the top of what I would call his forehead... it seems shiny and off color, but I can't get a good look, as he always follows me in a position that it's tough to see him in. Otherwise he seems incredibly healthy, and perhaps he got injured rubbing against something in my tank, I'm not sure. I'm keeping an eye on him though!