Why do baby chickens seem to have swollen and blue marks in the breast

[Googl]

My chickens are 2 weeks old and are healthy and free.
But in their breast area it seems swollen and with blue shaded areas.
Can someone explain this to me please.
They are broiler chickens.

 

[CoopCrazy]

Honestly I think that is were they stuff thier crops so full that it stretches the skin... My cornish x do that as well and had me freaked out .. They are bred to eat and eat and eat and I think your just seeing the crop full.. And they do have abnormaly large breasts

 

[Googl]

Thank you Coopcrazy, yes I noticed this morning that it was smaller...and yes all they want is food