When ever there is a health issue, it is always good to check with your Dr. - -especially if it is GYN related (to many differnt possible serious things happen down there.
With that said, I have often found myself with a "lingering period". . . the real thing ends and for a few more days to a week there is just a little to "wipe away", not even what could be called spotting. I did ask my Dr. about it and she said (both family and GYN)it is just your body changing (sorry that should be getting older) your systme doesn't clear everything like it use to and therefore you get "clumps" or "sort of spotting".
Probably not a reason to freak out, but as I said, it is always better to be safe and make an appointment or at least a phone call to someone who has your history/file. . . might mean an extra Dr. bill, but will also mean less stress and worry (which could also be a reason).