staining on blue stone

I just had a lovely blue stone patio, 2 in fact, installed. My contractor used a product called "gator dust" instead of grout/cement....whatever the more traditional material would be to put between the stones. Almost as soon as it was put in, the edges of many of the stones darkened, in some cases a rust color appeared on the edges. In some cases no discoloring appeared. They give the appearance of being stained. It is most unattractive and I'm wondering if you can give me any advice as to what products/solutions would be best to try to remove the staining or, am I stuck living with it as it is (I hope not. I have seen your advice for how to deal with efflorescence and thought that might be worth a try.) Thank you in advance for any advice you may be able to give me.