heatmiser
mr. green christmas
If you start removing stuff you could well start accelerating the problem. Pitting in brass is not so much of a problem but in cast metal which I suspect you have it will get worse if you allow more air and sweat or moisture to get at it. Essentially the cast is uneven in the distribution of the metal crystals as the alloy varies from place to place. A weak spot will get eaten away.
If I was you I would replace them and put the old parts in a dry sealed container wrapped in acid free paper with some silica. That is if you want to keep them as is for a resale.
The process of plating involves flashing a copper base coat to seal the casting, then building a base coat of nickel which levels out the polishing marks and introduces a bright shine. Finally chrome is flashed on top as it is hard wearing and stays bright longer than nickel. Anything not cleaned off before hand or any minute pits under the surface eventually result in pitting. Thats why lead free machining brass is preferred for plating on precision parts where longevity is required. it is significantly more expensive to produce though. Even replating cast metal is an issue as the process of cleaning and activating the surface for plating can make the pits worse. You can get by the problem by building up the copper base coat but that is time and problems.
Ohhhh...THIS POST...sorry! I didn't see this until now. Duh. Reading now....