I had a similar decline in health with my female. Old vet treated with antibiotics and gave me some mange shampoo, neither of which worked. Several allergy panels as well. After over $1000 spent to try and figure it out I switched vets to a guy that sees a lot of GSDs and Mals from some local PDs. He diagnosed it in about 10 seconds telling me she had a yeast infection and all the meds were doing was feeding it. Two shots of ivermectin two weeks apart, and some thyroid meds later she is a new dog. Coat's come back, all kinds of energy, looks great. She is also interacting with us and asking for attention sometimes even wriggling past my pushy male. Really a shocking difference.