Can you get a picture?
Your dog getting demodex isn't the breeders fault. All dogs have it, but a healthy immune system is normally able to fight it. My dog gets flare ups too.
Sarcoptic mange is the contagious type.
Momto2GSD suggested trying SeaVive which contains colostrum, in addition to many things, so I'm hoping it will help boost my dog's immune system. The one spot she had on her lip is gone, so I'm hoping it's helping, but they do seem to clear up after a time, so time will tell.
I feed my dog raw, to keep her away from any unnecessary fillers (she has allergies as well)
Is the spot with missing hair possibly from sleeping on a hard surface? They can get callouses on their elbows, but my dog was also getting the demodex there and I was getting pretty fed up with people telling me it was 'kennel elbows', when it wasn't. I know what kennel elbow looks like!
Can you try giving your dog a bath with an antifungal/antibacterial shampoo? I'm wondering if it could be something like ringworm?
Good luck! My dog does get the odd flare up, but they seem to clear up and are more infrequent now. **touch wood**