What output is higher...?

My friend has Oracle Alexandria with Grado ZF3 cartridge/Prelude tonearm. I assume that ZF3 is MM cartridge and must have at least 3mV output. Input sencitivity of the phono preamp Michell ISO is 0.9mV.
When I connected my reserve Benz M.09 to his arm and than to the phono preamp it sounded much louder on the same volume levels of preamplifier(Monolithic).
Listening to his setup with ZF3 I realized that there is not enough gain in the system giving a mushy dull and shallow sound but I couldn't understand why... Can the output voltage decrease within the age of a cartridge(7y.o)?
Or can I assume that the cartridge sustained a damage and needs a re-placement...?
A cartridge output could decrease for several reasons. Among these:

As the cartridge ages, the material used to suspended the cantilever could lose elasticity and limit the motion. This would cause a decreased output since output voltage is proportional to amount of motion.

Another reason would be that either the magnets have decreased in strength or that another part of the cartridge has become magnetized in a manner that offsets the original magnets.

In any case, cartidges have a limited useful life. Any idea how old the cartridge is or how many hours?
The cartridge is 7years old and probably has ?00,000 hours on it.
I guess this one needs an appropriate replacement.
What would be the good match 1mv or higher for the light mass tonearm?
Sorry, can't help you there. I have a Wilson Benesch set up that came as a matched set and I'm afraid I am not that knowledgable about matching arms to cartridges.

If you can get seven years out of a cartridge I think you are doing pretty well
Marakanetz, I think a Dynavector 10x4 Mk 2 would do fine on that arm. The Dynavector is not too heavy, has a compliance of 15cu and an output of 2.5mv. It should match up very well with that unipivot.