They have been deprived nutritionally, or some illness has not been picked up, or they have not been screened for vision or hearing defects, or they have not had some kind of a chronic illness or error of metabolism picked up.

Advertising Disclosure: Please note that many links to retailers are affiliate links, which yields a commission for us. allauthor.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon sites.