You can try Gritzo supermilk. It does not contain steroids as per label. It will have to be tested for steroids to make sure. Please meet a dietician for diet plan. You can give full cream milk. No supplement can guarantee making baby look plump. If the child is active, no need to worry. Weight is ok. Do blood test for
vitamin d level as he gets heel pain. If that is deficient, he may need supplements