They might be...the gray pattern is called birchen. The look skinny for lack of a better word. Are they young? Japanese birds are difficult to hatch...they carry a lethal gene connected with their leg length I think. Do they have short legs?
I just got them today they are a little skinny but ima try and fatten them up.. And yeah their still young pullets , they have really really short legs its actually kinda funny seeing them walk. The gray one does have the darkish legs idk why they look like that in the light ill take some better pictures