SEO Expert needed for quick advice

One of our sites is currently 4th (and 5th) for our chosen keywords, looking at OpenSiteExplorer, we have higher domain and page authority, and the sites above us seem to have been around for a shorter time, have less links, etc. We just need some advice (or explanation!) for why we are down in 4th, and any advice to get us up a little.

It's just a quick consultation we need, if you could reply with a really quick overview of your experience that would be great.