At those temperatures, have they been water sufficiently? At times a fridge can take enough moisture out of the chestnuts to hurt the germination and if we don't water enough then our germination drops way off.
I would take part of the ones that have germinated and pull them from the growing media. Squeeze them to see if they are firm as opposed to swishy. If they are firm, I would soak them in water over night (12 hours) and then put them back in growing media. If they are somewhat dry, the soaking can kick start them.
Notice I said part of them. Sorry for the bad germination numbers.
Wayne