Iridium plugs have very tiny electrodes, it may look wierd to you, but that's how they are.
Iridium is super strong and highly conductive; therefore it doesn't require a massive electrode.
You need to cut it with a special laser when making it into a spark plug. That engine block would melt before the iridium does.
Odds are, it's not melted away, that's the way iridium plugs are supposed to look.
Now if it's phisically melted, then something is seriously wrong... Why not take a picture of the plugs and post it so I can actually see what you're talking about. Is the ceramic insulation cracking? Is there a lot of carbon? Different signs mean different things.
Stay away from platinums, unless you have some special things going on under the Hood
. Iridiums are fine.