Sounds like Finny is just going through a phase then. I agree you could try to add something to his food to intice(sp) him to eat a little more. As long as he has a clean bill of health from your vet. then he is probably satisfied with the amount he eats. All dogs are different.And the recommended amount for food on the package is just that,recommended. It is to give you some idea of about how much they may need to eat.Just experiment a little and see what foods Finny likes. *Remember Onions and chocolate are toxic to dogs.*
Goodluck!

Angie