It's funny how that even with the normal lighting, heating and humidity that some frogs will still sense the seasons outside and I've heard this is due to the pressure in the air.

If you're concerned I'd definitely consider misting more, so the humidity stays around 80% stimulating the rainy season. I'd check out some books and go to the sections on brumation and health. Sorry I can't be of more help, I've not experienced this with my frog before but it's something I might read up on more just in case. Good luck and I hope your frog's okay