you can do it by two ways :

1- By using a soft white brush in photoshop and low down it's opacity and paint on the spot lights.

2-You can use a sphere around the spotlight and give it a white color then go to it's shader --> Effects --> Glow then give it a littile bit higher intensity as 0.2 then check the hide source button.

i think one of those will give you the effect you need.

Cheers