Are there not sucessive tests that the vet can do? Or is there a dermatologist that your vet can recommend? I don't know if it's ever been done before, but, I know I'd donate ten bucks (I know that's not a lot) to help with Jasper's testing if that's what the problem is, maybe we could help out or something. That sucks that those tests didn't find anything. Don't blame yourself, though, there's nothing you could have done to prevent this.