What are these weeds and how do I get rid of them? They're thriving in the dry soil while the grass struggles.
The last weed I think is creeping indigo. We live in Brisbane and it is everywhere - I have been painstakingly trying to cut off flowers before they become seed pods and dig out the whole plant - tap root and all. I have now been told that probably best to cut off at ground level and drip poison onto the tap root to really kill.
It is tough to see detail in your pictures but it looks like Lotus comiculata or bird's foot trefoil, bird's feet trefoil? Very invasive weed. There is a reason plants like this get labeled invasive weeds. They can out compete all other plants and thus stay vigorous, green and have kinda pretty flowers. Is it normal to allow your lawn to go dormant over there? Allowing a lawn to go dormant is the best way to select for those weeds.
Dormant plants just can not will not be able to compete. Do you have cool season grasses down there or warm? What is your grass species? What are your watering restrictions?
First thing to do is to continue chopping those flowers off before they go to seed. If they have already gone to seed, we can discuss how best to deal with this and we are not talking chemical herbicides...yet. Mow and BAG that lawn LOW to suck up as many seeds as possible. Put those seeds in a plastic bag to decompose, not in your compost pile. Never let this plant produce flowers if at all possible and you'll be able to eradicate it over time. You've got to get your lawn up to snuff or these weeds will be the greenest part of your lawn.
There are a few other ways to produce a lush competitive lawn. First off let's start watering your lawn deeply then allow to dry out before watering again. This promotes deeper root systems while most weeds are shallow rooted. Let me know the composition of your lawn grasses. Do you have a shop vac? I'd go out and suck up all those pods/seeds before trying to use the mower as a vacuum/pruner. When did you last aerate? Fertilize and with what formulation?