I think visible rib should be a sign of malnutrition because it is for humans. Visible ribs and protruding tummy in humans is a sign of a deficiency disease called kwashiorkor and it is common amongst children. Maybe you could study the nutritional value of your pup's meal. Or better yet place a call to the vet before your next appointment (i do not know if you can do that, I am just suggesting). In all I wish you all the best on the journey with your Pup.
Thank you for sharing #dreemerforlife