Most likely the change in soil quality, food quality, and bugs that come in from the food has interrupted your metabolisim. It could help if you research if Australia uses bromides as part of their food and textile industry as well, because the use of halides like flourine and bromine can interrupt healthy metabolisim. The solution to that is adding some (little bit, like 5-10 mg) Lugol's solution to salt baths.
Yes, australian foods can possibly be lower in minerals, especially if the agricultural traditions are quite different.
However, the answer to the problem is not adding more minerals and nutrients (via vitamin pills and tablets), because they are terrific gut-bug feeders that tend to make the source of ropeworms, candida albicans and other fermentatious bacteria, overmultiply.
If you're not struggling with metal dental fillings (elsewise you may be able to track your issues back to those), then a good dose of sulfur-rich cleanse may help start clearing out your issue.
The above link covers using an essential oil product to clear your system of bugs that have gotten a foothold on your health and made a party of stealing nutrition from you. Essential oils are the medicine from back in Jesus' day, and were used pretty liberally on both him and the other figures well known from those books! Prayer, nutrition-rich foods, and asking the Holy Spirit for guidance in how to handle specifically your personal needs should open the doors to what you need to win back your well-being.
(I say sulfur-rich cleanser because the PDF above points to a product which is VERY rich in sulfur oils. If you are interested in a different approach, the diet is always your starting point. :) Essential oil therapy can help you shunt the bug-colonies out, with patience and getting the dosages right. )