Not your fault at all, and you've been a good host! I didn't have any kind of 'participation rule' in the Pre 30s HoF or many other HoFs I've hosted. And that's because I kind of hate telling people you have to write a review once every 2 weeks or you're out...And I trust the core group of HoF members. But yeah dropouts are a problem especially when you rate until the end of the HoF to quit.
I think this is a good compromise (but it's up to the host of course):
I think this is a good compromise (but it's up to the host of course):