How to identify the issue in between task start time and endtime(act_hi_actinst)

Hi , In below actinst table having doubts with startime and end time .

We have executed more orders to test performance test.While debugging few orders,we got few subprocess took more time to start the service task. In below example one servce task ended at 2021-10-29 13:45:57.511 but another service suppose to start immediately .But here it took 7min to start(2021-10-29 13:52:04.161). Please help on dubug this issue.

I have attached the screen shot also.

In act_hi_actinst where proc_inst_id_=‘’

noneEndEvent 2021-10-29 13:52:04.299 2021-10-29 13:52:04.299 0
serviceTask 2021-10-29 13:52:04.268 2021-10-29 13:52:04.299 31
serviceTask 2021-10-29 13:52:04.161 2021-10-29 13:52:04.232 71
startEvent 2021-10-29 13:45:57.511 2021-10-29 13:45:57.511 0
serviceTask 2021-10-29 13:45:57.511 2021-10-29 13:45:57.622 111

is there any way to identify the issue(with any other tables help)with any other threads will it become slow.