get a thorough Vet physical to determine if the dog has parasites, internal, external . Might need a worming . Might be deficient because some worm is robbing him of nutrition.
Vet will determine whether there is a health problem , thyroid , hormonal problem .
Make sure you are feeding high quality protein , and a source of minerals , essential fatty acids.
Make sure you don't have an underlying bacterial infection or fungal problem on the skin to give you that musty odor.
lots of articles and suggestions in Dogs Naturally Magazine Dogs Naturally Magazine