No chance whatsoever of an intruder being responsible for their deaths, nor food poisoning, if it was an intruder the other 2 dogs would have ripped the intruder apart, GSD’s are fiercely protective of their owners
As she died not in the main bathroom but another one where the dog was I am thinking the dog hadn’t been well and she was checking in on the dog, giving the dog medication, the heater fell off and killed her by hitting her on the head, Gene may have been in the garden as he had sunglasses, hears a crashing sound goes inside and in a rush to get to her/find her, moving quicker than normal he falls over in the room he died in