Hi Cam,
Fertiliser is a confusing business.
Personally, I use the same ferts all growing season here. We don't have the same bitter winters as Northern hemisphere so there is no real need to feed trees for winter hardiness. I think most Aussies use the same stuff all year round.
To help flowering you can swap to a higher K fert ('flowers and Fruit', 'bloom booster', 'Tomato', 'Citrus', 'azalea', 'rose' etc are all very similar) in late summer when flower embryos are forming for the following spring.
Raw NPK numbers are not the only consideration. Dilution rates need to be taken into account. 10:6:6 diluted at 10 g/litre gives exactly the same nutrients as 20:12:12 diluted at 5g/litre so higher numbers will not adversely affect the trees if application instructions are followed.
I use Thrive soluble at 25:5:8 and Powerfeed at 12:1.4:7 most of the time and both of them give good results on all the plants I grow. I would probably be just as happy with any other complete fertilisers. Those 2 are just the ones I can get reasonably easily at good prices per nutrients.
You should be mindful that many native Australian species, such as Melaleucas, Acacias, Leptospermum, Syzgiums, etc are phosphorous sensitive so fertilizing with a high or even moderate P level can be fatal.
![Face Palm :palm:](./images/smilies/facepalm.gif)
Much misinformation about Australian natives and fertiliser. The genera that Shaady has just listed are
NOT P sensitive. All those love 'normal' fertilisers and so do most of our natives. Some of the proteacea family including Banksias, Grevilleas, Hakeas, Proteas and Lecodendrons
CAN SOMETIMES be sensitive to higher P but note that the last 2 listed are not even Aussie natives so I submit that the whole premise of Aussie Plants being sensitive to P is flawed. Just a very few of our natives can be and so can species from other parts of the world.