Hello, and thanks for your feedback regarding the Timberline cover. Often times when something like this occurs, it is usually the result of a cleaner that contains bleach or another chemical, which might also explain why the discoloration shown in the photo is so evenly distributed. For the best results, try wiping down the cover with warm, soapy water or a mild detergent, followed by a quick rinse. Of course, if you believe that this is the result of something else, please reach out to Traeger support so that an agent can go over the situation with you and see if something can be done.