Seth fiddles with his hands nervously while waiting for Gyre to respond again after the initial response. His gaze is pretty much anywhere except Gyre, though his attention is quickly jolted to his hands when Gyre starts signing again.
Too heavy? Oh...right of course that's what he'd probably figure.

Nervously he signs in response.
"N-no I, that's not it, I can move all of them just fine, I'm quite used to it really. Especially Miriel and Sophie, as well as Mary here, they always want to be looking over every little thing I do."

Yeah no, this, this kid was definitely talking about the puppets as if they were people with their own independent thoughts, even motioning to the puppet he'd been signing with before when mentioning 'her' name.