Low membership

I am a new member of a sorority that has just gone through formal rush without any bids of any kind. At the end of the semester we are losing 13 graduating seniors, this only leaves 17 collegiate members on campus. Our sorority has never been very good with formal rush but it has never been this bad. I am basically asking if anyone else has gone through this problem and corrected the problem?
Just to add more info. We have had little support from nationals and all effort has been on the members. The campus we are on is over 25,000 students. If there are any more questions please reply. Thanks
sarah