Has this huge rash like thing on his back, it looks like skin pealed, he's tan and the rash thing looks light pink, people say it's a fungal infection?

Maybe Tinea. Skin rashes are difficult to diagnose without actually seeing them, but this sounds as though it could be a fungal infection called Tinea Versicolor, which is really common but not harmful. It can be frustrating because of the skin color changes. It is most common in moist/humid/warm climates and more obvious when one is tan. It is treatable with many OTC antifungal sprays or with selenium lotion.
I agree. It is possibly Tinea Corporis. Sun tans will bring out these kind of infections as the areas will not tan as the surrounding skin. It would have to be seen to make sure.