Chicks not wanting to walk, all 3 of them

I have 3 baby chickens, all from the same mama, or so I was told from the feed store. I have been doing everything I can, reading books, feeding good diets, ect..., then suddenly this morning they all started not wanting to walk. They try to get up and take a few steps, then just sit down. They were fine last night about midnight, then at 7am this morning this happened. I bring them inside at night in a big cage, then during the day they go outside in tehir coop. They can walk but dont seem to want to I think. They are eating, drinking ect....
Please help, could it be worms? Is it a pesticide or anything? My landlord may have puts omething outside the coop though I seriously doubt that, she likes chickens too.
They just seem like they are weak you know, they sort of stumble towards their food. They can walk a few normal steps, then just sit, its so strange and Im very worried.
Anyone have any ideas about what it may be? I'll probably just have to take them to a vet, silly as its ounds, Im having trouble finding chickens vets where I am, that worries me also.
Thank you everyone so much for your help.