88 is probably not bad at all for six weeks. I have several Hubs in the 60's, but I also have others in the 70's, 80's, and 90's (so even though trying to get those in the 60's is a good idea, having a few won't hurt your score too much). Traffic (and getting voted up) helps each Hub.
I haven't looked at your Hubs, but some things you may want to try (if you haven't already) might be adding capsules (if you don't have too many), participating in the forums (so some people may click on and vote your Hubs up), do whatever you can to increase outside traffic, and read and add "real" comments (not just meaningless ones) other people's Hubs. There's lot of help on the site (on the forums, in Hubs, in the blog), so you could search for something like "increasing traffic". (Running spell-check can catch any typos that may cause readers not to vote up.)
Other than that (although I don't know, of course, because none of us really knows what goes into our scores on any given day), there's a good chance your score will go up in another few weeks (if not sooner).