Micromyrtus ciliata alba

[Kunzea]

Interesting observation on soil drainage. Without seeing the actual mix it is hard to evaluate. I say this because 'my mix', which is mostly used for natives, is generally viewed as being unlike nearly all others in that it consists of veg garden soil, with a long history of digging in compostables. I sieve this to remove the coarse bits and then add about 20-25% by volume of some mixture of coarse river sand, zeolite, pumice. Occasionally have used diatomite, but for some reason I feel unhappy with that as trees don't do well - soil too well draining! I use the heavier mix (garden soil may be a 5-10% clay/silt) in order to hold reasonable water, as it gets pretty hot and dry up here in Canberra. Most of the time, every drop is carefully used.
Not sure how all this can be related to your experiences, but I thought it worth flagging that the world of soils is far from easy .