My iphone 5 hairline cracked between camera and flash havent drop it

Hello,

I bought my iphone 5 month and a half ago. I noticed like 15 days ago a little scratch between the camera and the flash going through the mic. Now today I realized that the little scratch has become a crack. I havent dropped my iphone at all and i have pics to show that there is not impact signs anywhere. I was wondering if anyone else is going through the same issue. I found on the net a couple of cases similar to mine.