Got an SR500 myself and in the almost two years I've had it I have no tarnishing or oxidation yet.
I've heard these are notorious for losing their almost black coating though and it's the nature of the beast for them to look that way - but as an anecdote I always wax all my basses - and I mean all the time.
Wipe it down after every gig or jam and even practice.
I try to wax all my basses and guitars at least monthly if not every two weeks or so.
I think keeping things well waxed with a real carnauba bean-derivative wax is the best preventative measure.
Use
Meguir's Deep Crystal Carbauba Wax - Step 3. If the wax you buy says: 'carnuba' it's not real carnauba bean wax.
My 15 y/o bass looks new. All my gear looks new. I wouldn't have it any other way.
But I don't think there is a cure for this situation as I've head complaints on the
Ibanez site about the same problem and others say that with a little lovin' they've had no untoward problems so far.