Can you see visible marks on the glass that covers the camera? On my galaxy note the glass become marked, it happened quickly and it was almost like someone had dropped some super glue on the glass but I suspect it was that the glass was slightly raised out of the body and was being scuffed when you put the phone on say a table or desk. I was really careful with the phone as it was brand new and so can't think of any other reason. I could have sent it to be repaired but it would have been gone for about a month and I needed the phone.
What I eventually did to fix it was took some car scratch removing cream (cream that removes small scratches from car bodies) and rubbed that on the glass, it took a little while 20min of buffing but the glass slowly cleared and now photos are not blurred at all.