A Galah with a bald spot
I shower my Galah every day: his feather condition seems fine when he is dry, however I have noticed he has a small bald spot (about the size of a thumbnail) when wet on his chest. He goes into the shower with me and I use the shower head all round his body.
He doesn’t appear to be plucking or homing in on the area and it is hidden once his feathers are dry. He is eating healthily and very active - out of his cage between 5 and 6 hours a day.
I suspect that what you are seeing is a normal apteryal area on your bird. Most birds do not have a solid set of feathers everywhere on their body, and the central sternal area and that over the crop are non-feathered skin, or apteryal regions. When the feathers become wet, this makes them more visible.