Menstrual cup help

So I used a menstrual cup for the first time today and I had no problems with insertion or discomfort or leaking throughout the day or removal. But once I took it out i was smacked in the face with an awful like rotten smell... I have never had that smell come from me before so I am kind of freaked out. The cup, the blood inside of it, and my vagina all smelled like that though. But I didn’t smell it during the day or anything. Today is day 3 of my period and I haven’t had this until today. No weird discharge or anything either. I’m just wondering if anyone else has experienced this???

I did have it in for about 10 or 11 hours. The paper that came with it said I could leave it in for 12 hours.