Thanks for your query,
Complementary feeding is started by 6 months of age.
I suggest you to start with boiled rice water,vegetable soup,glucose
water.in addition to milk.
semisolid like cerelac can be started by 7th month .
By modifying her diet her stools will be normal.
In case constipation
persist get her evaluated by pediatrician
Wishing your baby good health