[Lukec]

Hi I've just took what I believe to be the original spark plugs out on a 1.4 fiesta duratec 2012 mk7 , the last plug had some oil residue at the bottom near the electrodes and elsewhere but not a lot and the conditions seemed a bit worrying they did take a bit of wiggling to come undone but I'm guessing this is Because of rust I tightened them up to 15nm , as per haynes manual specifications, could anyone tell me is this condition normal and could it indicate anything amiss with my engines internals?
Oh I do use injector cleaners occasionally apparently this can result in some brown tinges on the spark plug
Thanks