I just called another vet here in town who was on the news as having treated some of the affected dogs, and she said that the symptons show up quickly, and if mine have been eating the food for a few months, they will be OK. She also said I could go to my vet and have blood work done to check their liver, which reminded me that we did have blood work done on our dog that was sick last month, and everything was good.
I'm still thinking about tossing it just so I don't continue to worry
but at least I do feel better now!