how to re-harden mints

[CanadianJohn]

I bought a large bag of mints from a bulk-food store. They were fine at first, but have now become too soft, despite being kept in a plastic bag.

Does anyone know how to re-harden mints?

Fridge?

overnight in the fridge makes the mints harder, but nowhere near hard. I'll continue my research.

Dehydration or pop in the oven to dry them out? I've no idea really but according to Google moisture in the atmosphere makes hard candy go soft.