Subject: How does vinegar react with silver plated utensils?

An AP chemistry student noticed a funny taste and discoloration on her grandma's 
silver spoons.  She said these had been used "forever" and it never happened 
before.  I suspect they are plated.  Did the silver wear off and the offensive 
taste is from the metal underneath?  Is there an electrochemical process that 
incluces the tarnish, (silver sulfide?)  She said the discoloration goes away 
after it is cleaned.  But it all comes back when used with vinegar.  Thank you 
for help.

Re: How does vinegar react with silver plated utensils?