I have a 2011 suburban 1500 LTZ 4x4 and I did a tune up back in 2022 and replaced all the spark plugs. It is now Jan 2025 and I have driven about 20,000 miles and two of the spark plugs started misfiring. I didn't know what it was right off the bat but the check engine light came on and it was idling rough. I took it to a local shop and they told me two spark plugs were misfiring. I had them replaced but it has only been about 2 years and 20K miles so the mechanic was saying it may be an indicator of a bigger problem and I needed to take it in to Chevy to have them check. Before I go I would like to try to get some Idea of what I am dealing with so I am not walking in blind.

I have attached a picture so you can see. Could this just be a bad sparkplug or bad spacing or does it look like something else is going on here.