I have the D800 that I bought about 4 months ago and I noticed that I am not able to get sharp images consistently. I am fairly new to this hobby so the camera is mostly left in the P mode and auto focus. When shooting stationary subjects I do not get sharp focus in all the pictures. The lens I am using is 18-300/f3.5 VRII. The camera is set at AF-S and and is set at 51 points of focus. Where should I start to troubleshoot this problem. My wife believes that the camera was more consistent when we just bought it.