NB stopped updating some twitter feeds

[2nerdscom]

I just noticed that two of my twitter feeds stopped updating themselves three days ago.
I’ll attach a screenshot of the site settings showing how everything was hunky dory 'til the 17th, when the polling appears to have just stopped.
The poll on the 20th is when I manually selected “parse this feed”.
There may be more twitter feeds that were affected; I just happen to have noticed two of them so far.
I’m holding my breath to see if NB resumes normal polling now or stops on its own again.
“Friends and Followers” says my twitter account is still connected.
Are there any clues to be had about what’s going on?

[2nerdscom]

To clarify, I have many other “1 subscriber” twitter feeds that did not stop updating, so it doesn’t seem to be the case that something was wrong with my NB account’s NB-to-Twitter interface. It’s odd how the stoppage is hit or miss.