Are you a smoker keep your car inside the room. Cigarette smoke can easily turns all blister to yellow and other factor like direct sunlight even strong odor. If car we keep it tightly inside the box and still turns yellow than maybe blister chemical mixture is wrong somewhere. Keep carded car hangin to the wall for long period like 1 year plus also can turns all carded car to yellow as moisture and light is big enemy to blister. Never smoking with your carded car around. My E.D and IT G.M room is so affected with cigarette smoke as they are trouble smokers. All fabric furniture, wall paper, curtain even air cond blower unit turning yellow! I have to change curtain and sofa fabric every two years due to cigarette smoke.