Been having a weird issue with my female WTF

[tsume24]

So some quick background -- I have three White's tree frogs: Herp, Derp, and Burp. Derp is the only female. I've had Herp and Derp for six years, and have had Burp since last July. Herp was once treated for an intestinal parasite (4-ish years ago), but that's the only health issue I've ever had with any of them, until now.

For the past couple of months, Derp has been spending 99% of all of her time in one of the hides I have in the cage. I literally never see her come out, and if I physically take her out (at night of course, when they'd naturally be awake), she goes right back into the hide within ten minutes. She still eats just fine -- she always lunges at the tongs when I hold them close to her face. But she just...doesn't come out. Ever. A couple nights ago I was surprised to come home to see her out, sitting on a piece of driftwood decor I have on the floor of the cage, with Burp hanging out on her back (that's his favorite spot, so I guess he decided he was sitting there whether or not it was occupied, lol). I can't attach the picture for some reason, but I did post it here on Reddit: https://www.reddit.com/r/reptiles/co...at_stack_last/

I'm just... sort of baffled by the behavior and can't think of what might be causing it. I know it's not Burp's presence because she went like six full months paying no mind to him. I keep their cage clean, always clean their water bowl, feed them regularly, mist when needed (which is rare), their temperature is good... it's like she's super sensitive to light, or something? But her eyes aren't cloudy, no blemishes on her skin, nothing. If anything, she's just really fat, lol... but not so fat that her ears are covered; I've always watched out for that. She wasn't always like this -- she used to sit on the highest perch in the cage every night. So, yeah, any insight would be wonderful, cuz I'm not sure what to do. I'd take her to the vet if she appeared sick, but she doesn't.

Here's the cage specs:
18x18x24 exo-terra terrarium (will soon be upgrading them to a skyscraper terrarium that's a foot taller)
substrate: ~2" of eco earth coconut fiber
temperature: 77F
humidity: 60%, usually a little lower
lighting: 26-watt UVB during the day (mostly for the live pothos plant), 25-watt "moonlight" bulb at night

[elly]

I'd put it down to personality differences or being a little too warm. My larger frog has always been shy. When he takes a cricket he immediately hops away.
Keep an eye on her appetite, though. Make sure she's not sitting int the waterbowl all the time. Maybe lower the temperature slightly too if the tank doesn't automatically become cooler at night. Also watch to see that the other frogs aren't snapping at Derp all the time.

[tsume24]

I never see her sit in the water bowl, ever. But like I said, her skin seems just fine to me, so maybe she's soaking when no one's looking? I'm not sure. And, these guys never bite at each other or show aggression in any way. The "worst" thing that happens is when they sit on each other, or when two are trying to squeeze into the same spot in the bamboo tube in which they sleep during the day, and they croak out of annoyance. But that's it.