You are so very in tune with your little Archie. I guess even with early stages of renal failure they must have groggy days when the toxins back up in the kidneys.
We've just bought some 'Greenleaf tablets' by a company called DENES for our foster girl it's a traditional herbal remedy for symptomatic relief of arthritis, eczema and kidney complaints. Ask your vet if this might help any?
Hope he feels better in himself soon.......