Noticed today that with a couple of the soft toys our puppy has, he'll chew and chew at them, and eventually make a whining sound. He's 8 weeks old, and only got him yesterday. This started this afternoon, and agin about 30 mins ago. Is this because he's frustrated with he teeth coming through, or just excitement? I'll give him a harder toy, but he'll switch back to the soft one and make a noise again.