Think im having a few different problems with my lawn.

My garden was in two parts it was recently extended and new lawn put down. The new part has gone all brown round the edges. I have also noticed some mushrooms growing but no near the brown bits more in the middle where there are no brown patches. Does this mean the brown patches could be fungus? Also i seem to have other brown sections around the other parts of grass. The part near the fence i put new soil down and seed but no grass grew at all which it normally does when i fix brown spots on the other lawn. Ive included a picture of when the grass looked better to show what i mean by the two lawns.

 

Have you got a dog? Bitches pee will burn the grass.

 

Yes but ive never had issues with my grass like this and have had the dog for 10 years. Plus i dont allow them on the new lawn so that cant be causing the brown on that bit.

 

Could be several things, there's something called red thread which ironically causes brown patches. When you say newly extended, how long ago and what was there before?
If it was uncultivated before it could be wireworm leather jackets or Chafer grubs, all of which will eat roots and cause brown patches. Birds such as starlings coming in more than usual might indicate leather jackets (crane fly or flying daddy longlegs larvae) .

 

Another possibility - have you moved the things that are standing on the grass? You can get brown patches under things like seats, the feet of swings, etc where they block the light and rain.
Brown areas round the edges could also be due to rain shadow from fences etc. I don't think grass right up to fences/walls works very well generally. It rarely looks good all the way up to the edges.
Yet another possibility is that there could be some unevenness in the soil underneath the grass. More free-draining areas/patches, or places with buried stones/bricks etc, will turn brown faster in dry weather.