From 6 months of age in addition to milk solid food should be started as milk is not sufficient for the optimum growth of the child. From 1 year family food can be offered to child but it should be soft. Solid food contains dense calories and causes growth of the child and you can add some edible oil or ghee to child food to increase calories. Pediasure usuallt advised after 2 years of age in addition to solid food and not a single source of food. For immunity you give all balanced diet which consists carbohydrates, protein, fats and oils, vegetables,leafy vegetables and fruits and regular immunization
to your child. Because of excessive consumption of cow milk child will develop anemia
and this causes low appetite and fussiness. So restrict milk to below 500ml per day and try to give soft solid family food.