my kid is 23 months old but according to his age and other children he is very slow and weak physically as well as mentally, what supplements can i give him?

A. he is very weak ... gv wt gain foods as potato sweet potato ragi dalia banana avocado pumpkin dry fruits as cashew almonds walnuts in paste or powdered form ghee butter cheese in moderate amt.. start with vit supplements as zincovit..