Bought BM Dresses But Not Mine At DB

My bridesmaid`s bought their dresses from DB, but I haven`t committed to buying mine from there yet due to the large downpayment they require. Since they got their 15% off, and I didn`t get my dress there yet? Will I have to pay the difference (are they no longer entitled to the 15% discount) I didn`t pay any additional downpayment for the dress, but promised to get it there. Since that time I found the same dress for less elsewhere. Any ideas? Thanks for your help!