ORIGINAL: crenshaw
check your peep. It could be that your peep is turned slightly. If thats the case it will cause your pins to be seen as blurry. Also, if you have a small peep that doesnt allow much light in during low light situation it will make it harder or blurry too.
x2 - I had this problem last year, the serving holding your peep in just may have started to loosen up, or the rubber cord that aligns your peep may be getting stretched out and not turning it all the way.