I'm not sure of she was under fed.
I have a male Coastal that's not putting on size as quick as her.
When I get home ill look at my records and give you an idea of size they both have out on over the year.
I'm not sure what I would do in your position.
The breeder might just be hiding the fact that he already knew but I would let him know what's going on. Maybe send a video. Just in case he really doesn't know.