Blood clots no Period

*** ASKING ON BEHALF OF MY WIFE *** MIGHT be TMI ***

My wife wiped and was pink which she thought was her period starting on 11/9. BUT she has not actually bled or leaked at all on a pad or anything, since the 9th she has been passing small dark almost brown blood clots, rarely wiping any actual blood and if it is it’s from the clot itself. Her periods are usually normal, until this happened. She had our son almost 2 years ago and she is definitely not pregnant or TTC, no birth control, no diagnoses of PCOS or endometriosis or other underlying issues. It’s been over 2 weeks since it’s started and we’re most likely going to schedule an appointment with our OB but we’re curious if this has Happened to anyone before?? If so what brought it on?