I don't think they will think you were a bad pet parent because of that. I don't know what breed your last pup was, but I believe I've read some dogs as well as cats are prone to certain illnesses.
Heck, people just up and die from heart attacks, who have never had heart issues, so I think it happens the same with pets.
There are only two rules at my house: House rule #1. Cats rule. House rule #2. See rule #1.