builders: If you really think it's not a linking problem, make sure everything on site is good. Make sure Google can access the site. Make sure you're not inadvertently keywork stuffing, and are keeping duplicate content limited or non-existent.
If you do all that and find it to be unproblematic, you'll need to start looking at your backlinks. Luckily you're in an industry where there's pretty much a built-in readership base, so get starting writing guest posts, creating resources on your own site, and generally promoting the site.