Oil Stains

I was doing quite a bit of laundry today - including all my bed linen.  And as I was putting the fitted sheet back on my bed, I noticed that it was covered in quite a lot of what looks like oil stains.  Like the kind of marks that get left on your clothes when you spill some oily food on them.  These spots definitely weren't there before.  This isn't the first time I've seen something similar on some of my stuff when it comes out of the laundry, which I why I've got loads of stain remover, but never to this extent before.  Weird.  I wonder if something is wrong with the washer or drier?  Either way, it's kind of annoying - especially on clothes when I only notice the stain on my top after I've been wearing it most of the day...