help in marketing on preForeclosures

Hi everyone,
I been doing short sales for almost two years and i never had a problem with marketing. I did direct marketing and the responce was great i would send about 500 a week and get around 10 phone calls and sign up around 2. But lately for about 3 months allready i get very few calls and most of them are not even good leads they responce ether i took care of that problem or iam not in foreclosure stop sending me letters. I check with my leads provider and they said that everything is good on their end. I have no idea what am i doing wrong or maybe their is to much competision now. Please anybody give me some advise …