I have corrected the birthdate at the page of one person.
But in all other entries it is not corrected.
So comes the message "Child Born before Mother"
and in this page I can not correct the birthdate.
You will need to open the record on each child and when you are in the child's record you can click "Edit" and it will open a Window that will allow you to correct the child's birth date.
@Tom123 is right
Here is another tip, there are 3 icons placed to the right of the "trashcan" icon. They are shortcuts for copying information into other fields without having to type each one individually.
This is useful if the children have a slot for a mothers birthdate and they all have the same mother. Then you can just use the shortcuts to copy and paste that value from the first entry to all other entries.
Im not sure if that will help you here in this situation, but maybe in the future.