Thanks for the tips so far, guys. Anything I haven't tried yet is worthwhile.
@Momto2GSDs: Yeah, it hit them both literally at the same time. As in within 24 hours. And since it was not unreasonably long after opening a new bag of food, checking for a formula change was one of the first things I looked into.
And treats are another no-no where Brody is concerned. Very, very rarely and always the same brand. And since I live alone, I can pretty much guarantee that no one else is giving them anything -- again, unless they've learned to treat themselves and are VERY good at hiding the evidence.
Thanks for the suggestions about the food. If I need to switch, I'll definitely look into those.