A.M.
My son's pediatrician told me to not start baby food until 6 months so that his stomach had all the enzymes needed for proper digestion (or could create stomach problems later in life). Also, one thing I have done with my son when he only drinks 4 oz from his bottle (I know he is hungrier but is often distracted) is offer it again in about 5 minutes. He often will drink more. Then a little later, we eat solid food, so that he gets all the formula he needed first and then the rest is from solid.