If one charger is charging one or more cells a little more than the other (your 4.23 reading) That could explaine the difference in mah. Unless the batteries get unreasonably warm during a charge I wouldn't worry about it. It's easy to over analyze this stuff at the price we gotta pay.
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It's "Dr. _paralyzed_" actually. Not like with a PhD, but Doctor like in Dr. Pepper.