I think it's more not "Are they sick?" than "How sick are they?" They ate the food too, and while they didn't eat most of it (Br was greedy as usual and ate about half of each can) they certainly did eat a good deal. All four IGs downed a case or two of the stuff together, and they all haven't been feeling very well.
Hopefully they'd recover from that sooner rather than later: they aren't sick enough that we would take them to the vet if we weren't fairly sure that their kidneys are damaged.