AGM Battery Voltage

Hi, I am in the Panama Canal Zone and have bought here a new Deka AGM battery. (MK 8A 27 92Ah) I use it as starter battery in my sailboat. 

When I charge my full bank, house batteries (800Ah) plus starter, the whole bank stays at 12.85V when no load is put on it. The new starter battery by itself, disconnected (that means absolutely no load) goes down to12.69V. (Environment is very dry.) That seems too low to me for a new AGM battery.
I'd be very glad if I could hear your opinion on this.
Thanks and regards,   Chris