Hi... I don't think its a male dominance thing. If one dog has an accident in a multidog household, you'll often find, they
all will start. Since now there is a new potty area!
What did you use to clean the spot? Natures miracle or other cleaners made specifically for accidents are what you want to use.
Its possible your new dog has a urinary tract infection. This makes it so they can't hold it. It would be a good idea to have a vet look at him.
As far as the D.A.P.. i haven't used it, but i know that the cat version is very effective, so i doubt its too big a rip off.
Start from square one, and be consistant about a schedule and you will probably get better results
Good luck