Hair loss and black patch on dog snout

Hi all!

My 3 year old Jack Russell, Penny is currently at the dog sitters as I have been away for quite some time. I have been sent a picture of her and she seems to have a black patch with perhaps some hair loss near her nose.

Does anybody know what this could be? I am returning home on Saturday and will take her to the vets but would be nice to see if anyone had any insight earlier?

I have also attached a pic of what she usually looks like

This was penny only last week..