I have an iPhone 5s. I just purchased two new cases, and when I put the first on I noticed the spots. I took it off, they disappeared. I then tried my second case and the same thing happened. I have 3 other cases and none of them have ever done this, also I've had my phone about 3 years and nothing like this has ever happened. So why are these cases causing yellow spots on my screen? Is there a way to prevent/fix this? Is my phone broken?