Yea that is pretty common. The plate on the cap does "wear in" and you will develop some new colors on the metal, as well as some slight dimples. The Lotus does not care and will still perform wonderfully.
If you tend to combust more often, you can remove the plate and hold it to a light. If you see pin holes in it, then go ahead and replace it. The plates are consumables and all have to be replaced eventually, but if yours develops premature cracks or holes, it is easily replaceable in a matter of minutes.