(SOLVED) PHP MySQL data to CSV file. Missing first row of data

I'm able to export the CSV with the heading and data (only if the data consist of more than 2 rows). If the it only has 1 row of data, only the header will be displayed and not the values. I'm not sure why. There's nothing wrong with the codes - can be compiled and run. Most likely to be code logic, but I don't see it.

  function exportCases($export_company, $export_day, $export_month, $export_year) {
    $dbMgr = new dbManager();
    $conn = $dbMgr->getDBConnection();

    $queries = "select * from case_report where ";

    if($export_day != 0) {
      $queries .= "day(start_date) = ".$export_day; 
    } 
    if($export_month != 0) {
      if($export_day != 0) {
        $queries .= " and ";
      }
      $queries .= "month(start_date) = ".$export_month; 
    }
    if($export_year != 0) {
      if($export_month != 0 || $export_day != 0) {
        $queries .= " and ";
      }
      $queries .= "year(start_date) = ".$export_year; 
    }
    if($export_company != 'default') {
      if($export_day != 0 || $export_month != 0 || $export_year != 0) {
        $queries .= " and ";
      }
      $export_company = "'".$conn->real_escape_string($export_company)."'";
      $queries .= "company_id = ".$export_company;
    }

    // Fetch Record from Database

    $output = "";
    $table = ""; // Enter Your Table Name 
    $sql = $queries;
    $rs=$conn->query($sql);

    if($rs === false) {
        print "<br />";
        die ('Error in executing query: '.$conn->error);
    } else {
        $rows_returned = $rs->num_rows;
        if($rows_returned == 0) {
            return null;
        }
    }//end else

    $columns_total = mysqli_num_fields($rs);
    $firstRow = mysqli_fetch_assoc($rs);
    $fields = array_keys($firstRow);

    // Get The Field Name

    foreach($fields as $r) {
      $heading = $r;
      $output .= '"'.$heading.'",';
    }
    $output .="\r\n";

    // Get Records from the table
    while($row = $rs->fetch_array()){
      for ($i = 0; $i < $columns_total; $i++) {
      $output .='"'.$row["$i"].'",';
      }
      $output .="\r\n";
    }//end while

    // Download the file

    $filename = "myFile.csv";
    header('Content-type: application/csv');
    header('Content-Disposition: attachment; filename='.$filename);

    echo $output;
    exit;

  }//exportCases

EDITED: added the foreach() code.

    // Get Records from the table
    foreach($fields as $f) {
      $output .='"'.$firstRow[$f].'",';
    }
    while($row = $rs->fetch_array()){
      for ($i = 0; $i < $columns_total; $i++) {
      $output .='"'.$row["$i"].'",';
      }
      $output .="\r\n";
    }//end while