I forget how fast my frogs grew when I got them as babies. I know in the past Wabo, my big male, has put on weight very quickly, but I couldn't give you a rate. Just make sure he isn't putting on weight quickly because he's feasting nightly on wax worms
. That'd be like eating a bowl of twinkies for dinner every night!
As for calling, it is perfectly normal for 3". Below is a picture I just took of Mushu, who is 2", and has been calling since I brought him home. Of course his calls don't have the deep bass Wabo's have, hehe, but that'll come in time.
Good luck with your WTF, maybe you could post a picture for us! 

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0.1.0 Normal Leopard Gecko: Mala Ala
2.1.0 White's Tree Frogs: Wabo, Chabo, and Mushu
0.1.0 Bearded Dragon: Igor
5.0.0 Betas: Ghost, Fruity, Misty, Assasin, and Cobalt