That's nothing my 2011 is at 40.99 AHr and 62% SOH with 60,080 miles. (still 9 bars) My guess is Nissan dropped the AHr threshold during the 2013 software update. Especially in the Bay Area and other colder climates.
I've been following this thread for months now since I lost my 3rd bar somewhere around 55,000. Now I'm almost at end of warranty 59,887 miles and my 9th bar refuses to drop. My Leaf Spy Pro numbers are: 42.34 Ahr 64% SOH 43.35 Hx