My son is 9 month old . He had good social skills when he was 5 months old . ( used to look at us when we call him , also smiles when he look at new people. Used to be very happy when he look at kids ) . But now it has reduced a bit . He does not respond /turn around on calling his name . However he is happy on looking at kids. But does not react to elders . Is it a concern ? What can I do to improve his language n social skill