jQuery FullCalendar下一个按钮不显示周视图事件（ajax）

I'm working on a calendar that fetches data from an immensely populated database (more than 10,000 records). This has made the application extremely slow to load.

In view of this, I am trying to implement via AJAX (json) a search for weeks.

I've already been able to load the current week via AJAX, but when I click the prev or next buttons, the adjacent weeks are empty.

From what I read in the documentation, these buttons would continue sending the startParam and endParam variables, but this is not happening.

My code is jammed and full of php patches, but it works perfectly, except for this slowness.

Jquery:

events:{
url: '../ajax/entrada_agenda.php',
type: 'GET',
dataType: 'json',
data: {
        startParam: <?=strtotime($FirstDayWeek)?>, 
        endParam: <?=strtotime($LastDayWeek)?>, 
    },
}

,

And in the PHP page I make a select with the dates sent (already converted to UNIX).

SELECT * FROM agenda_marcacao WHERE DATE(data_do_agendamento) >= '".$data_start."' AND DATE(data_do_agendamento) <= '".$data_end."'

$data_start and $data_end are variables populate like this:

$data_start = date("Y-m-d", $_GET['start']); 
$data_end = date("Y-m-d", $_GET['end']); 

Is there any way I can indicate on the prev and next buttons these start and end values for weeks?

Because of what I see, FullCalendar will not interpret that I want to pick up the events of the weeks only when prompted, not the entire database ...

Any help will be greatly appreciated, thanks :)