I would feel anxious too! I had one person who didn't send in their reference for months (I had submitted my application way early). What I did to 'remind' them was to send an email saying something like, 'there is still plenty of time before the deadline but I just wanted to make sure you received the link of where to submit your reference'. It worked because she submitted it within a day or two of me sending that email. She also apologized for taking so long.
I think the key is to maintain that balance between generally following-up and nagging. If you've sent an email within the past two weeks, I'd suggest you go with your gut and not send another email until at least the beginning of December.