
The pattern isn't typical, but might be worth having a thyroid test done by your vet. Usually, however, with a thyroid baldness you get it affecting the flanks , but anything might happen, I suppose! They may also recommend taking a skin scraping or allergy test.
You could try spraying with colloidal silver solution - I cured a thin, but not really bald, coat in son's 9 year old neutered flatcoat by spraying with this for a couple of days, and the difference had to be seen to be believed!
Hope you get it sorted
Jo and the Casblaidd Flatcoats