Brown patches on lawn

New lawn professionaly laid around 9 months ago to our new build home, used turf on a roll. Initially it was a lush green colour, unfortunately there was some slight gaps between the laid rolls, this was filled with kiln dried sand and seed. It was after this that the lawn took on brown patches. Treated twice with gro more lawn treatment, Not the 4 in 1 weedkiller version, as have no weeds at all. Doesn't appear to have made any difference. Reading this forum and elsewhere, my conclusion is that's it's likely under watered, having never seen a lawn like this before, I feel in the need of confirmation of this.

In case it simply does needs more watering, I have put out the sprinkler, to give it a good soaking.

Attached photos
Thanks in advance

 

Possibly as you say down to the dry weather.
Did you water the fertiliser in well.
Is your mower nice and sharp.

 

Yes could be
Yes
Yes

Thanks

 

Are the brown patches mainly near the gaps where you filled with the kilned sand?
Kilned sand can absorb and retain heat, to much can cause scorching in hot weather, and we have certainly experienced longer and warmer days this year. I would of recommended filling the gaps with a lawn dressing, a mixture of soil and sand. I also don't think the lawn has not been watered enough, we had very long periods of constant sunshine and no rain this spring, which will have put stress on the newly laid lawn if it wasn't watered regularly enough.

 

Can't fill the gaps as they are no longer there lol
Am going on a heavy watering regime before winter sets in
Thanks

 

I did not say fill the gaps, I asked, is the browning where you had filled them with kilned sand?