They are on loose coarse litter mulch, beneath black wattles. The ruler in each photo is marked in inches.
This morning, 31 January, I see the yellow patches are now beige and larger. Yesterday's beige patches look browner and have not expanded.
Fuligo septica is common on litter and mulch of all kinds. In fact, it can be found developing on stones particularly after rain when the litter layer is wet. The yellow becomes beige and browner with maturity, then when more rain or even just a leaf may fall on the brown mass, a distinct brown cloud of spores is emitted to be spread around for future development. Insects and small mammals will also disperse these spores.