
I was thinking thyroid problem, sometimes test results come back normal if the levels are borderline, might be worth having another test or at least getting the sample analysed again if that is possible.
I don't know very much about pet foods as I feed my dogs a raw diet, but I don't think Hills is one of the best foods. I'm sure someone will be along soon to advise.
Adding flax seed oil and vit e oils help with the coat so it might be worth adding these supplements too.