I don't have any experience with this, and have never heard of this happening after surgery. I had my male Dozer neutered 2 months ago, and everything went fine, he healed quickly, and pees normal like before the surgery. I am sure someone else on here will be able to help you soon. It's quite puzzling though, and funny that its both dogs and not just one. I wonder if it a territory or marking thing, since its both dogs. Do they both live in the same house? If it keeps up, maybe you can ask your vet if they have ever heard of this. I hope you find a solution soon, and it's nothing too serious. I can see where it would be frustrating though having them pee in the house. Good luck, and keep us posted.