they're old
Properly aged I'd call it like an old wine or ripe cheese! Whatever floats your boat. I'm sure the shopkeeper was glad to finally get rid of them. They must have been on the shelf for donkey's years to get crumbly.
crumbly
Hard ot describe - not crumbly in the sense of going into crumbs, but they kind of melted in your mouth without the jaw-sticking gooeyness of some krówki. Never thought of them as being old, stale or at or near the expiry date but rather as one of two different types.