my two had the exact same symptoms during the recent hot weather only thing I could think of was that they weren't getting enough water from their bottles .so put in a bowl of water and they drunk it dry so kept two bowls of water in the hutch and the ferrets were right as rain after a few days
shocked to hear that esox , bought alot of wet gear about a month ago and the big tall one not the wee grumpy one told me they were moving to benson st , shame