[Maximo]

Are they scratching only at their jaw, or other spots too?

If only the jaw, I would suspect something related to eating and drinking is affecting them both. What kind of bowls/plates do you use for food and water? Plastic can be an irritant to many pets. Some dogs will react to stainless steel. We switched to glass custard bowls for water and porcelain plates for food. Make sure dishes/bowls are cleaned daily, after each meal.

Another possibility is that the jaw is always wet and allowing yeast to grow. Or perhaps they are reacting to too many treatments to the jaw area?

Max had a couple of dry black spots on his chin near the lip line recently. I wasn't sure if they were normal because I never looked that closely at his skin there before. I gently scrubbed them during bath time and made sure to dry his chin well. The black spots went away.