im australian as well, living in germany, for the last 2 years ive been moving back n forth n it has played a number on my hair. i got tighter curls, 3c, though they do get bigger in the australian weather. maybe you have build up and need a good sulfate to start anew.
it may be worth saying, that due to my change of climate all the time, ive got my routine down pretty simple and only really use naturl stuff. i use a bought cg conditioner and low poo. apart from that i only use conditioner oil styling n thats pretty much it. i dont know if you wanna give that one a try. but do a sulfate normal shampo wash first n see if that helps.
ooh yea argan oil is great! just make sure that its pure argan oil, cause they mix it with alot of silicones so if its got silicones in it then that might be your problem.
pure argan oil is one of my favs.

my hair: 3b, high porosity, high density and coarse hair (i think i finally figured that all out)
my hair loves conditioner only styling!
Oils and my own procuts are my hairs best friend
my hair goal length is bra strap length when curly.