Hi @mimimoore0811,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
There's a good chance that these areas are experiencing some issues with drainage and getting air down into the soil where it is needed.
I'd suggest that you dethatch and aerate these dead patches. Start by using a thatching rake to pull out as much of the dead grass as possible. After this, use a garden fork or aerator to break up and aerate the soil.
Check out How To Dethatch Your Lawn and How To Aerate Your Lawn.
After this, apply a buffalo-safe fertiliser such as this Yates BuffaloPro Lawn Fertiliser Hose On Off and ensure you water and mow regularly to maintain a healthy lawn.
Let me know if you have any further questions.
Jacob
