HELP - Sir Walter Lawn doing it tuff

[Samc81]

Hi 

looking for a little help identifying the problem with my Sir Walter Lawn which was installed in April 2019 in Sydney.

It was looking amazing and healthy up until around mid November after a couple of really hot days a few large patches turned completely to ‘hay’ in a day or so

Since then I have been trying to nurse it back to life with doses of seasol and watering but it is still patchy with random green shoots. The dead patches are pretty solidly connected to the soil with what I’d imagine are root and it doesn’t lift up like some people describe when the lawn is infested with grubs but the patches are slowly spreading. See pic

 

Lastly I some of the grass where it is healthy is sprouting for lack a better tern and I’m not sure if it a weed or just because I have let it grow see pic

 

I’m not sure if I have a Grub and weed problem or just need to be patientand wait for it to bounce back. Any advice would be great

[MitchellM]

@Samc81 Terrific result!