Strange crust on chicks belly?

[WAChickens]

So recently just a few days ago I got 6 baby chickens from the store(yes the store, sorry if you get offended but it's the only way I can get them) I got two white EE but one of them has a strange spot on her tummy. It is quite rough, but so far it hasn't affected her in any way. She's the only one that has it too, I just can't identify it. What is it? Sorry the pics bad i may post another one if it can't be identified.

 

[junebuggena]

Umbilical area. It's normal. Just leave it alone.