English Springer spaniel hair thinning and pigment loss

Two trips to our local vet and we have ruled out all the big players that would show up on blood work. 2 separate thyroid tests, Cushing’s syndrome, cancer… all blood work and urine is normal.

He is 8 now and his hair started thinning 7 months ago. First on his back and now it’s his whole back, down the sides and up his neck. He also used to be dark liver (brown) and the part that is thin is also very light brown now. When hair does grow it’s very patchy. We did melatonin for 3 months per the vet with no luck, also doing fish oil and vitamins. Still nothing.

Next step is a dog dermatologist – however, I would love not have to spend the money and make the trip downstate to do that. Besides his appearance change, he seems healthy and fine.

Any diagnoses ideas or treatment ideas would be appreciated!

This was taken 1 year ago after a summer haircut:

This is the current situation: The darker patches on his back are the random hair that is growing back. The light brown color hair isn’t growing. The white fur on his legs hasn’t been affected. It’s still long, soft and white. The white fur on his neck, chest and belly are thin now and has an off white color.