bald spot under chin and white tips on feathers

My black bantam australorp has for some time now had a bald spot under just under her beak on her chest. I have noticed one of the others  (very occasionally) pulling her feathers out at this spot (and she doesn't seem to mind). In addition the very tips of her feathers on her head have turned white/grey so she looks like someone's tipped oat flakes/porridge  on her  .

I think she may be just starting to moult now but this condtion has been going on for months. She is fine otherwise.

Any suggestions as to what the problem is?

I haven't noticed any mites/lice on the bald spot.

Thanks for any advice you can give.

I've had her over a year and she was about 12 weeks old when I got her.

I pretty sure she should just be black all over. The rest of her feathers are fine it's just the ones on her head. It doesn't look like it's part of her natural marking. Just looks scruffy!

Thanks for the advice