I can only give you my own advice - and I'm no expert - so I hope you can get your zero hubs back on track!
With my poorer performing hubs I:
change a title,
add a new video or image,
rearrange a few capsules
take a look at the tags and summary to see if I can improve them.
When I'm in the mood I also look at SEO keywords and experiment with longer tail keywords ie little strings of keywords that make sense and just might bring in some traffic.
Sometimes when I go back to some of my older hubs they can seem a little tired so I have a go at refreshing them using all of the above over time.
Also make sure Google and Bing are crawling your site by checking out the stats!