What is wrong with my chick?

[Bacongirl27]

here is a picture of my chicken two days ago

and here is a picture of her today

I know the lighting is different but it is the same chick.
What is causing this?
Does she have worms?
They are approx 4 weeks old and I noticed that her crop is enlarged.
All of the other chicks look fine, and she is acting normal.

What do think is wrong and what should I do to fix it?

 

[Imp]

Could it be lice or mites?

http://ohioline.osu.edu/vme-fact/0018.html

Or maybe losing fluff and growing feathers?

http://www.oznet.ksu.edu/library/lvstk2/mf2308.pdf

Any other symptoms?

Good luck,

Imp

 

[wyliefarms]

is the crop hard or squishy?