Help! White's Tree Frog not eating?

I have 2 WTF's ("Blue" and "Brownie")that I have had for 6months to 1 year. Both were eating and seemed fine. I had them in 2 separate 10 gallons and upgraded to one 29 gallon (live plants, cocofiber substrate.

For a while now I never see Brownie. I have to literally dig him up to check on him. I don’t think the tank is too cold though cause Blue is eating and walking around and soaking normally. Anyway, I dug up Brownie to check on him and he seemed a little thin to me. Not horribly emaciated, but definitely thinner than Blue. So I decided to separate him. I place him in a 10 gallon with damp paper towels and a Under tank heater. I gave him a water bowl a little hide and 10 crickets. I even turned the lights down since he tends to be shy (but not off, I wanted to watch him) 2 hours + later he has not eaten 1 cricket. He even had a cricket on his head and didn’t eat it.

Anyone with experience with frogs have any idea what might be going one or what I can do to get my froggie eating?