It can if it's progesterone related which yours probably isn't if your day 21 was 44. However, they should check you out just to make sure nothing else is causing it. I've had spotting for 3-7 days before my period for about 15-20 years, they did various tests and all fine. My 21 day bloods came back as 60.8 so also good. I've actually been pregnant twice in the past 8 months (both losses) and on those months I had no spotting at all. So for me, it doesn't seem to be a problem.
I do think you should push for a few more tests just to be sure. I was referred to a gynae and she did a hysteroscopy to make sure everything was ok.
Good luck.