I know that you have a specialized shampoo, but for my thin-furred dog that battles staph off and on, this has been a great shampoo for us:
https://www.amazon.com/Vets-Best-Spo.../dp/B0002AQMAA
My dog has a collagen disorder which affects many things, including her ability to grow fur. She is on thyroid meds which help, but it's an entire syndrome. Homemade bone broth helps. You might look at try a little bit of zinc and biotin. You don't want to have increased zinc for too long, but if it helps, it means there is a deficiency. Huskies are an example of a breed that often need extra zinc.
With my girl we didn't turn a corner until I took her to a dermatologist and I started her on oral allergy immunotherapy. Drops instead of shots.