7018 electrodes are designed to be low hydrogen electrodes.
But if they are left out in the atmosphere for too long, they are no longer low hydrogen rods.
But that doesn't mean they are no good.
You can still use 7018 that have not been kept in an oven for anything you would weld with another rod like a 6013 or 7014.
Of course they weld better fresh out of the box or oven.