What would these bald spots be due to?

[beetlebug]

I just noticed she’s red and has lost feathers here. Is this possibly normal molting or something else?

 

[aart]

How old is bird?
Does she sleep on a roost?

 

[beetlebug]

She's about 1.5 years old. I cant seem to spot any mites or bugs anywhere on her. All of the other girls seem to be completely fine. Yes, they roost at night.

 

[aart]

Does bare spot go farther back than pic shows?
Might be from 'roost rub'.
Some birds just have more brittle feathers that can break easily.