From the looks of it, your plugs look like they are running just fine. The rust has no effect on the read of the plug. I can't see it in the photograph's you supplied, but you may consider paying real close attention to the top portion of the ceramic just below where it meets up with the center electrode. You should be able to distinguish a lite colored brown ring (otherwise known as the fuel ring). If you can see this, your plugs are doing just fine. If not, well, it means your probably running a little lean.
Also, take a look at the ceramic. It should appear to be flat White in color. If it is glossy in appearance, it means the ceramic is getting too hot because the engine is in fact running a little too lean. If you can get a magnifying glass and a light. Go ahead and shine a lite down the spark plug and look in there. Make sure the ceramic is White all the way to where it meets the metal. If its sooty, it means you are too rich.
The best way to set up and read a spark plug is to bring your plug wrench with you and go out for a ride for about 30-45 minutes and while you are riding look for a safe place to pull off the road. Then kill the engine and coast to a stop without idling. Park the bike and let it cool down for 10 minutes or so. Remove the plugs and read them or put in a fresh set and bring the ones you just took out back home where you can in fact read them.
HD plugs should only cost about $2.50 ea, right?
The other guy who stated the center electrode is worn on the edges is correct. The edges of the center electrode should be sharp and crisp corner. Hope this helps.