New Spark Plugs - Tune Up

I did an oil change with 5w-30 Mobil conventional oil and replaced the spark plugs this weekend. My first time trying the NGK V-Power Spark Plugs, model number: BKR5E-11. I wanted to thank everyone for the insight on copper plugs. I'm running a 2003 Elantra GLS, California SULEV version, with 185,000 miles. This was long over due, its been about 5k since my last oil change and about 40k since the last time I replaced my plugs. Previously I had the Iridium LX NGK's in and those were so expensive at about $10 a pop, these are working smoothly for $2.95 a piece. I noticed my transmission shifts are much smoother, can't believe I drove with such bad plugs.

I noticed the plug from cylinder 2 is a bit darker than the others, could that be a head gasket issue on that part of the block? Or maybe running rich?