I've read on another forum of a lady who is losing a number of her pigs as a result of her using Nedz Bedz as it contains Eucalyptus Oil which is toxic. Fine for horses but not for guineapigs. She's had a post mortem which said all the signs pointed to Tannin poisoning which is in Eucalyptus. Please check you're not using this bedding or using any other bedding that's intended for horses which contains Eucalyptus.