8 kgs at 10 months is not underweight. Millets are good for health but have a low glycemic index.
Instead of fancy or exclusive diet, give the baby regular home cooked food that rest of the family also consumes. Without any added salt or
sugar.
A balanced diet consists of 4 equal parts of fruits, vegetables, grains, protein.
Give
vitamin d3 and iron supplement if not given after getting a hemogram.
Get a general check up from a pediatrician to rule out any pathological or physiological causes.