Hi everyone.....Our house is only 4 yrs. old but on one side of the tub where the sunlight hits the tub from the glassblock window the jets are yellowed - on the other side of the tub where no sun shines on them directly they are still white. It isn't real bad but we would like to find something to whiten those back up with & the product from the place we bought the tub from isn't doing the trick. My DH thinks the sunlight did it. I haven't used anything harsh on the tub so am trying to be careful & not do anything to harm it. It is the cover itself & inside the area on about 3 of them . Thanks for your help!