The 10/8 and 10/15 sailings were each school holiday weekends in different parts of the country, but I don't know anyone who had days off around the 10/22 sailing so it might be it wasn't as well attended as the prior two weekend sailings.
I do wish we had a "here now/just back" thread on the cruise forum like there is in the theme park forum and like there was for the UK sailings--maybe the mods will add one.