I tend to notice that my WTF gets more sluggish in the fall/winter and is not as active as he was in the summer. Even when I turn off the lights he doesn't get up and become active, until a few hours later or when I am in bed and not making any noise. He's already started to get into the "lazy" mode, as it is starting to become winter. This could be the case with your frogs.

If I were you, I would keep an eye your frogs just to make sure nothing is wrong. Make sure they are eating, keep the right temperature and humidity levels, and look for anything unusual, such as abnormal appearances or behaviors that indicate something is wrong.