You just contradicted yourself... but that's not why I'm responding anyway, haha. A proper setup doesn't always account for winter dryness. A humidifier is not a bad idea if you think that the air is too dry, I just wouldn't siphon it into individual tanks, that would be excessive. You could always just spray the enclosure.
Personally, I have a humidifier in my bedroom for me, but all the animals get sprayed occasionally and that's been working fine, no need to overly complicate things.