yellow crusty stuff on 2 dwarf quail?

[spish]

i got some quail yesterday and a lot of them (the hens?) have balding on their backs, on 2 i have noticed a yellow crusty looking something where the new feathers are growing. anyone any idea what that is? something to be worried about?

 

[Eggcessive]

I would include ages and post this on the quail forum under other backyard poultry for more answers.

 

[spish]

i posted in the quail part and no one knew what it was so thought id ask here they are (supposedly) 3 months old