The battery looses a few % of capacity rather quickly in the beginning. That's normal. Dropping down 4% in the first 6-12 months is common. It slows down from there on and stays mostly linear. Don't worry too much. It seems dramatic in the beginning but it will be fine in the long run. I know the 90s have a faster degradation problem, but I'm not sure when the 75 packs where introduced and if they got the same cells as the early 90s.