Has he been pooping lately? With two or more frogs in one tank its near impossible to tell who's poop it is. I would recommend getting a fecal done as well. My male sometimes refuses food in what I like to call "mood swings" but somehow manages to stay fatter than the female who eats everything. He's usually back to normal (by that I mean lazy but not lethargic) within a couple days. Although I think that your frog might just not want to move during the day. After all, if someone brought my dinner at 2 am I wouldn't want to get up. How is the temperature in the enclosure? Humidity?