3 week old chick won't grow at all with distended crop? (Pictures)

[lilyashlyn]

I have an almost 3 week old (will be 3 weeks on Thursday) Silkie chick who hasn't seem to have grown at all except for his wing feathers just a bit. It eats, drinks and poops fine. And it has plenty of energy. It actually eats more then the others. The biggest white one is a little over 4 weeks. The other two are about 3.5 weeks. It's crop feels very full all the time and seems to hang down a bit.
Any idea what's wrong with it? Will it not make it? Also is there anything I can do for it like vitamins or something?

 

[Eggcessive]

About all you can do is make sure that it eats and drinks, and putting vitamins and probiotics in the water 3 days a week may help boost immunity.