coil

Hi guys so I wanted to replace the spark plugs on my Apex, and 2 out of the 4 plugs this is what I found!! Sled has 4,300 miles on it runs great, just wanted to replace the spark plugs. Why all the rust around the spark plugs/ coils? What is this from? Note the coils where fully seated down on...

Pulling off some very stuck coils and one broke off inside the well, right at the gasket seam between the valve cover and the head. Anyone have any tricks or tips as to how to extract this thing? Thanks! Greg