Hi @RB16,
A warm welcome to the Bunnings Workshop community and thank you for your question.
I'd suggest having a look at the following articles for some general information:
Was your lawn brown before it was cut? Or did it go brown afterwards?
When cut lower than grass is used to, it will often go brown before bouncing back stronger than before. It actually looks to be in fair condition, it is just in the repair stage right now.
An application of lawn fertiliser such as this Munns Professional 2.4L Green Dominator Lawn Fertiliser Hose-On will do a lot of good.
If you have some weeds in your lawn, Weed n' Feed is a good option that will control the weeds and fertilise the lawn in one application.
Outside of this, mowing regularly at a consistent height will train the grass on what to expect so it will not have a stress reaction like it currently has.
Alongside this, watering consistently, especially on the hottest days will get your lawn growing beautifully.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
