There were some minor stat changes to a few pokemon recently, including Alolan Diglett and Dugtrio. Either the IV calculator/info is out of date, or the pokemon you have is showing the wrong stats.
In this case, it looks like the pokemon itself is at fault for some reason. A power up/evolve should correct the pokemon to the current values.
https://twitter.com/SerebiiNet/status/1073065805431083008