Oil or Antifreeze on spark plug ?

So I just got done changing my spark plugs for the 90,000 service. I noticed the middle plug on the driver side wasn't tight when removing it. After pulling it there was something on the plug at the base and porcelain. I don't know if it was oil, antifreeze or compression residue from being loose ? This engine hasn't missed a beat, no oil or antifreeze use and the plugs look almost like they did when I put them in at 60,000.
Any ideas ? Thanks

 

Got pics?

 

No, but still have the plugs. I can take a couple.

 

Here's a few. The plug on the left in the photo of all six is the one.

 

Unburned fuel or spark plug tube seals leaking. Looks more like fuel though

 

What does it smell like?

 

I completed my 60k service and found some of that tarry stuff on the end, not as high on the porcelain though. Another odd thing was the gap on all plugs were .050 instead of the .043. I read something about used plugs being that wide.

 

I didn't smell the plug. After giving some thought I'm thinking it's un burnt fuel from the plug being loose.

 

Found the same thing on my plugs at 60k.