Sporadic slowness

[eluser]imorris[/eluser]
Here's my welcome/index:

Code:

$this->output->enable_profiler(TRUE);
        
$this->benchmark->mark('my_mark_start');
$this->load->model('Member_model','',TRUE);
$this->benchmark->mark('my_mark_end');
        
$this->benchmark->mark('my_mark1_start');
$data['Members'] = $this->Member_model->get_members();
$this->benchmark->mark('my_mark1_end');

$this->benchmark->mark('my_mark2_start');
$data['checkins'] = $this->Member_model->get_last_ten_checkins();
$this->benchmark->mark('my_mark2_end');

$this->benchmark->mark('my_mark3_start');
$this->load->view('welcome_message',$data);
$this->benchmark->mark('my_mark3_end');

Here's my profiler:

Code:

Loading Time Base Classes   0.0080
My Mark   0.0023
My Mark1   0.0041
My Mark2   0.0013
My Mark3   0.0007
Controller Execution Time ( Welcome / Index )   5.0368
Total Execution Time   5.0448

My question is...My total profiler controller time is 5 seconds but my "mark" time is less than one second. How can I find out where the other 4.5 seconds are coming from?