I recently got a White's tree frog named Morty. I don't have experience with frogs so I'm learning as I go. Today I came back to Morty on the glass of the terrarium. As he was moving about, a trail of this mucusy stuff followed (from around his belly) and stuck to the glass. I've attached a picture for reference. I picked it out with tweezers and it all came in one strand. It did not move. He did defecate today, is still active and has been eating well. I'm afraid something is wrong. What is it? Is it normal? Or is it signs of something worse like worms or possibly its entrails? I love Morty... Please help!

Edit: also, he is croaking off and on at night. I feed him a mixture of meal worms and crickets. Hope all of that helps.

Edit 2: might have just answered my own question but I want your opinion. Shedding? He has gotten big since I've got him.