When we got our ex-street cat from Dubai checked over the vet mentioned he had a bit of gingivitis on one side, recommended crunchy dry food and suggested we tried to clean his teeth (hah!)
This week I noticed he was drooling a bit on one side, then on Friday he didn't eat his breakfast so took him to the vet expecting maybe a minor problem but he's got severe periodontal disease and will have to lose most of his upper teeth on the right side of his jaw. He's had ABs and painkillers and goes in for surgery tomorrow
The vet is shocked at how quickly it's deteriorated in such a young cat (he's only 4) and there is a possibility it could be being caused by something else so he's having blood tests as well
He is obviously feeling v uncomfortable and is uncharacteristically quiet - he even let the puppy lick his tummy 
Any ideas why it's got so bad so quickly? Poor thing already has (mild) asthma