Karen, if you can somehow relay to the owner, advise them to do toxin tests on their dobie, paying particular attention to kidney function - likewise, a urinalysis can detect oxalates that are common with some toxins. I'd even go a step further and do clotting tests or rule out autoimmune disease (causes could be many). If they or the vet suspect in the least possible food, they could consider testing a sample - (look online for similar complaints for the brand or type in question). Only thing is, if there is no manufacturer suspect at this point, the lab fees are the owner's choice/responsibility.
I think it should be priority to investigate the home/yard/any areas all the pets had exposure to (process of elimination, all of the pets could have ingested or been exposed to one thing, what could it be).
Another rule-out, generic or store-bought flea products, particularly topical. As you know, brands like Hartz and Sergeant's etc are notorious for causing very ill pets and fatalities. Also antifreeze, etc.
This is such a tragic situation, I so feel for them!
Dog rapidly losing weight
Re: Dog rapidly losing weight
..........Traci