Moving from Melbourne to Brisbane due to croup and asthma

Hi sisters I am in need of advice.
We are a young family with 3 children (5,3 and 10 months) My 5 year old and 10 month old suffer from asthma and croup severely every winter my daughter gets croup at least 4-5 times. She takes a preventer and regular ventilon as per respiratory peaditatrian. We have tried everything ( probiotics zinc vitamin C etc) to help them improve however nothing seems to be working other than regular steroids. (Prednisone)
Hubby and I are thinking about moving from Melbourne to Brisbane as we have heard and read about the improvement of manging asthma and croup. I was wondering if anyone has moved up to Brisbane and noticed a difference with asthma and croup. Any info would be greatly appreciated. Thank you