Is this happening with all the different instruments or only certain ones? At the factory the pianos and all the other instruments are sampled in their own ranges and they don't go up to the entire 128 note MIDI range all the time either.
Also if we are talking about C7 to C8 on a piano voice, I might have to ask, "How good is your hearing?" Old timers like myself tend to start dropping notes at either end of the spectrum due to plain old age.
If this is happening with all instruments, including synthesized ones, then you might want to seek out a second opinion in person. It could be early onset hearing loss and could be easily verified or dismissed by another set of ears.
Either way, it's probably nothing major to worry about.
Gary
