Hello this is our first time owning a full-blooded Bernese Mountain Dog we've had a couple mixes in the past. we got her as a rescue from someone who bought her at a pet store and decided they didn't want her. we adopted her when she was 4 months old and now she is 7 months old and she only weighs 53 lb. she hasn't grown like we thought she would or like our other bmd in the past. we have all the paperwork from the people that originally purchased her and everything's in order she's AKC registered but she's just tiny. is this normal? we're feeding her she eats great she's not skinny by any means she's just very little and short and petite. Her height (ground to back) is only 22in.