90k service - spark plugs

I have a 2017 Limited Crewmax and just hit 90k. I paid for the majority of the service (coolant, brake fluid, p/steering, trans, diffs & transfer case) but decided to do the spark plugs myself.

Overall the job wasn't too bad. Clearance issues got me a few times with getting a spark plug socket in there. I'm looking at the spark plugs and most seem to be pretty evenly worn. There is 1 I would like a 2nd opinion on. The spark plug on the passenger side nearest the firewall looks to have some caramel coloring on 1 side of it. I took pictures & hope someone can tell me why this 1 looks a little different.

The first picture shows all 8 old spark plugs. The 2nd picture shows the last 3 with the end spark plug rolled over so you can see the discoloration.

 

It's not unusual to see slight variation in combustion deposit from one cylinder to the next. My preference is to see all of them like one on the right. Imo, those plugs are exceptionally nice for 90K miles.

 

Thanks JohnLakeman - your reply makes me feel a little more comfortable about this. Appreciate it.