Give your local vet a phone and ask their advice not worth doing any harm to your ferrets, but its funny how as one of the previous posts says that you never get any pork in tinned pet foods
Your a top bloke mate, and i hope the wee dog turns out to be the best 100 quid you ever spent, great to here she is getting back to herself and showing her own character.
My brother has just went through the same problem as yourself told him to change the grub he was feeding to a better quality food and he has never looked back its worth a try the only other thing i would say is get the pup out your room as when you kennel it outside it might start again because its on its own hope all goes well mate.