Chicken size?

[MtnBiker]

We are new to chickens and recently got three chicks. They were all hatched on April 26th, so they are about 4 weeks old now. One of the three is now over twice the size of the other two. Even her feet are huge! She is so large (fat) that she cannot balance on a perch while the other two jump up and down and roost just fine. I am beginning to wonder if there is something wrong or if the smaller two are bantams or something. Any ideas?
The smaller two are a gild sex link and a Silver laced wyandotte. The big girl, who we now call butterball is supposed to be a buff araucana.

 

[Percheron chick]

The larger bird could be a meat bird. Bantam chicks are 1/2 the size of reg chicks at hatch so if they were all the same size when you bought them, they are standard chickens. Give us a picture.

 

[MtnBiker]

Chicks were all the same size when we got them. I have tried to upload pictures but it does not seem to be working for me for some reason?

 

[MtnBiker]

 

[Percheron chick]

Cornish cross.

 

[MtnBiker]

Ah-ha, so that explains her size, fast growth and huge feet/legs. Chicks were purchased from a feed store about an hour away from us by my parents, so we did not pick them out.