Have you tried asking your members what ways to boost the site? Suggestions? Have you advertised on other social media sites? When I had my Dolphin site I reached over 35,000 plus members before shutting it down. I used to get new people joining everyday. UNA sites seem to only pop up if you put in your sites name in search engines. Before with Dolphin you could type in meta keywords and your site would pop up even if it was 2nd or 3rd page in search engines.