измените свой sql следующим образом
$sql = "SELECT sum(col_1) as col_1_sum ,sum(col_2) as col_2_sum, sum(col_3) as col_3_sum FROM table_1";
и получить
while($rows = mysqli_fetch_assoc($run)){
$col[1] = $rows['col_1_sum']; // in here its better to start this $col[] array's index from 0
$col[2] = $rows['col_2_sum'];
$col[3] = $rows['col_3_sum'];
}
или как этот массив $ col начинается с 0-го индекса
while($rows = mysqli_fetch_assoc($run)){
$col[0] = $rows['col_1_sum']; // in here its better to start this $col[] array's index from 0
$col[1] = $rows['col_2_sum'];
$col[2] = $rows['col_3_sum'];
}