Could be a calcium problem, do you have them on the layer pellets? Do they have oyster shell available?
This article is a great read on egg quality ~ https://www.backyardchickens.com/a/common-egg-quality-problems
Did you find this egg in the nest box or coop? Looks like you may have an egg eater and they have pecked at the egg to get to the goodies inside. Was the egg empty on the inside?