Why does my roo become bald?

[Quail Lover 1987]

My roo was fine yesterday. This morning, he becomes bald (picture). He stays by himself in his cage. So no bird pecked at him.
Also, my male 3 weeks old chick lost his head and body feather, looks like someone pecked at him but doesnt show any blood like the roo on pictures. He is only in the cage with another female chick, and they grew up together, got along well, I dont think she pecked at him.
My other 6 quails are fine.
My cages are covered by 1/2-1/2 inch hardware cloth.
Please give me some idea what cause this to prevent. Type of Predator??? I dont want to wake up one morning and see my birds are killed.

 

[JacinLarkwell]

He hit or cut his head open. If he had other birds with him, I'd say they scalped him

 

[Quail Lover 1987]

He hit or cut his head open. If he had other birds with him, I'd say they scalped him

So no signal of predator here? This is what I worry the most.

 

[Nabiki]

He's either getting pecked, or he's hitting his head on the top of the cage. It doesn't look like a predator.