Hi Kristy,
The first thing I would do would use the tool here called Open Site Explorer and or use link:yourdomain.com to check all the sites linking to your site. loosing domain authority could be for a number of different issues but one could be some bad or non relevant links linking to your site. I would also use Google webmaster tools just to check the general health of your site and request a SEOmoz Crawl of your site. All of this data combined will give you a good starting point to what might be going wrong. I see you have a google page rank of 2 at the moment, what was it before?
Hope this helps.
Kindest Regards,
Craig
