Sorry I didn’t read that part. Mine have always gone away before I’ve worked out a treatment, I always have trouble sourcing medication for birds. Looking at the picture again yours looks more extreme than anything I’ve had, maybe it’s not the same but similar.
Sorry this isn’t much help.
I’ve seen this often in certain strains of my Brahmas, funny it’s only my blues but that might be a coincidence. Never seen it in other breeds, don’t know if Brahmas are more prone to it. It goes away after a week usually, but make sure to monitor in case.