Emma, something interesting happened. The backup ran again, and as before, showed each one was skipped. However, on the backup reports, the date for 2 of the courses (the ones I actually changed), was for today's date, the rest were for May 7. I did as you suggested and tried to restore one of the courses I had made an insignificant change to. It restored successfully.
So it looks like the backups are being done the way I'd like, I'm just not getting emails every day like I used to, and the report says skipped, even though the date has changed.
Thanks in advance,