I've been monitoring this on the way to & from work each day, looking at all the Plane trees in Carlton & Treasury Gardens - and my analysis is this: Things were at their prettiest early last week, and this week the leaves on the ground are less bright, and the trees are just starting to look visibly bare. So, I would get onto this post haste!
The colour in the Dandenongs is pretty much past its best. You're about 10-14 days too late. Add to that the strong winds last week and it's time to think about moody monotones...