Did you buy other kribs at the same time? Just be aware that if you bought a group of fish, they will no doubt be siblings so when one dies, the rest will not be far behind. People sometimes think they have some sort of disease in the tank when all their neons, or barbs etc start dying within days of each other but the other fish seem fine. It is just that they are all a similar old age.
Sorry about your fish. One of the fish I lost recently in my thermostat accident was an 8 year old BN.