my baby is 1.5 yr , she only have 4teeths. her teething was too slow from the initial stage. her tooths erupted All-together 4 at a time with upper jaw having 2(came together) n at the same lower jaw 2teeths where also coming, but not to full length till last month. I don't know why her toothing is sooo slow. is it any deficiency or something like that!?