Get rid of the Male canines and get yerself some female canines. I have a female miniature American Eskimo and my nieghbor has a male American Eskimo dog. The spots on their yard are aweful and all over. I don't have one dead spot in the yard, except where she digs, but that's another story for another day.
I heard that there is a chemical in a male dogs urine that kills the grass whereas it isn't present in a females urine.