She looks sick though. :-/ it could just be the pictures but... I have a bird with dwarfism (I guess how bantams started?) and he never hunkered down like that. He ran around like all the other crazy little ones, except he was the littlest.
Have they had any outside exposure where she could have picked something up? Post on the emergency board, maybe, see what those people say.
If she's had some exposure, I'd put them on liquid corid as a start for five days and look for improvement. Corid, as a note, does NOT work with ACV so don't mix those two.
That's only for cocci however, so keep an eye on her for anything else.
Are her nares dry and clean? Does she make the same noises as the others? How's her curiosity? Does she favour a heat source more than others?
Keeping her warm, dry, clean, well fed and watered is the best course. My dwarfed roo hung out under the heat lamp for much longer than the others. Now at night outside they huddle all around him. So cute. Bunch of big, fat, fluffy hens and this teeny tiny rooster head sticking up out of the middle.
Best of luck! Keep us posted, please.