Yes, it is probably due to the new page styling that Hubpages are testing under certain subject headings. Some of my Hubs are affected by this and took a nose-dive in page views and income, but after a few weeks have started to pick up. Of my hubs that are not yet affected by the page styling change, the page views have not changed.
Hubpages are testing these changes so I am sure they will be happy with any feedback on the effect it is having on your hubs, so let them know via “Contact Us”.
To quickly tell if your hubpages are subject to the restyling, the hubscore has been removed from the Hubpage (was next to the Hub-title) and the vote “up” & “down” buttons have changed.