For about two weeks now our pup Rufus (8 months) wakes up between 5-6am to throw up some foam. Sounds like he's hiccuping to start with and he may only throw up once or twice at most. He seems fine afterwards and wants to go out to do his business, then comes back in to eat as usual. He typically eats about 6:30 or so. No problems at all throughout the daytime. Any ideas?