Sorry, I can't answer that on just photos, I'd be going with Apache's suggestions.
ALthough - if you run your fingers through the coat against the hair, is is smooth or does it feel stubbly. If the latter then the hair is being nibbled by your dog, in which case, make sure fleas are not a problem - treat dog and house. If smooth, then other possibilities exist and I run some tests. GIven the proximity to the fire, it's not singed is it?