Lower flight speed


first, please apologize my bad engish.

When using the flight plan with an DJI P3A during summer (good light), I was able to get very good orthofotos.
Now (November) I get very bad results.
I asume, this is because of the ligth conditions.
Dronedeploy increases the ISO-value, the result are blury images.

Can I change the flight speed ?
By flying with lower speed, the shutter-time could be longer und the ISO-value perhaps stay at an accepteble low value.

Is there any way to do this?