Help me diagnose? Mites?

[BrentChicks]

My girls resist being handled but have captured this on camera. Can any of you help diagnose this feather loss pattern? It is mites? Thanks in advance for any ideas!

 

[GodLovesU]

Could they be molting? If not, I would check around their vents for parasites.

 

[LaFleche]

You can easily grab them from the roost at night for a close inspection.
From your picture alone there is no way for us to determine what exactly is causing the feather loss of this bird.