Add More Field Validate

function education_start_end_validates(array &$form, FormStateInterface $form_state) {
  foreach ($form_state->getValue('edu_education_field') as $key => $value) {
    if($value['start_date'] > $value['end_expected_end_date']) {
      $form_state->setErrorByName("end_expected_end_date", t('Education : End/Expected End Date should be the greater than Start Date.'));
    }  
  }
}