Maybe it's allergies. One dog we had that had to live outside was allergic to everything green and growing. If she did not have a bladder problem she could have been a housedog. We gave her the smallest dosage possible of benedril. One pill a day - that's what our Vet told us to do. Otherwise never give human medicine to an animal.
Your best bet would be to take them to the Vet for an exam and find out exactly what is wrong. It might be something they got into. Do your pets visit each other?