I understand and it's good cause for suspicion! Her mugshot makes her look guilty! Lol. :lau
She may also have a stronger immune system, different bathing habits etc.
How are your roosts set up.. are they allowing for this butt picking?
To me plucked feathers don't make for angry skin.. I do...
That may be true.. but what I see there is caused by parasites.. classic location angry skin the whole cha cha.
Treat with Permethrin (horse fly spray) and don't pluck anything.
ETA: a small spritz directly to the skin of each bird.. feathers parted, soaking not required.. under each wing...