It sounds as though it might help you to have a national officer who is skilled in rush come in - specifically one who has gone to your school or one very much like yours, since what works south of the Mason-Dixon may not work north of it, & vice versa. You need to get out of the mind set of "everything was so great a few years ago and now it sucks." All sororities have peaks and valleys and no one is going to be on top all the time.
When you say some of the new pledges "don't fit in and don't help to boost our rep" - well, the first one you should worry about more than the second, because if you are taking pledges just to get numbers, it is not going to help them or the sorority. Don't concentrate on taking the campus queens or the prettiest girls - look for the girls who are most excited to be a part of AGD.
A summer or late spring retreat is a good way to get everything out on the table. If there are any internal problems the rushees will pick up on it right away. Work those all out before rush begins - you might all end up crying at 3 AM, but if it strengthens the sisterhood it is worth it.
GOOD LUCK!!