paws hurt/lymph node swollen

I do cat/kitten rescue and one of the individuals who adopted a young male cat contacted me regarding her pet. She stated "Buzzie" had a temperature, licking the bottom of the pads of his feet which seemed hot to the touch. She took him to our mutual Vet and they gave me metacam. They did a lab panel and found nothing however 1 lymph node was swollen and an external ear infection. This is an indoor pet where the pets are the 2 peoples lives. They have 2 additional cats which are not experiencing this at all. The vets are somewhat stumped! Has anyone else been through this? Your help would be greatly appreciated!

are they all eating the same thing??

Did they culture the infection???

I don't think they did a culture. The pet owner stated that his ears appeared "crustie" on the outside and this was the diagnosis by our Vet. Of course our local Vet did ask about going outside, getting into chemicals, etc.. and none of that is a possibility. Her house is immaculate and none of the others are experiencing anything like this. Any suggestions on the bottom of the pads of the paws hurting? I have not experience this with any of mine. Les