Help with my lawn

In need of some help with my lawn. Basically I've dug up concrete in my back yard and put a good 6 inch covering of low grade topsoil down which I then fertilised and seeded. This was the start of August. The grass is growing very well on the whole just patches missing should I just seed these patches again and hopefully they will grow or should I do something else ?
Cheers

 

I would seed the patches. This can be done up until mid-autumn or in mid-spring.