What do you mean they are being treated in the tank they are in? Are you putting medication in or what?
If you are stop treating them, do not use any medication or oils at all, especially if a petshop advises you to do so. Many fish medications are toxic to axies. If you don't have the time due to studies, then they will suffer more. I know this can't be helped, but the only way your axies are going to get better is make the time, otherwise they all may end up the same way as Bubbles, which by the way I am sorry to hear about.
Yes, you can empty the tank 100%. Clean it out properly, ie rinse everything, you can use a combination of baking soda made in a paste and rinse with water. Don't add any chemicals or soap to clean it.
Keep the tank floor bare apart from caves etc..., simple is better and while the axies are ill probably a lot less hassle for you to clean and you can spot uneaten or regurgitated food.
When you do place them back in the tank, just make sure to do partial water changes EVERY day, regardless of how tired you are! Leaving it for 10 days and then doing a waterchange, even a major waterchange causes more problems (stress leading to fungus, of which you're now well aware of) than anything esle. Make sure to always use dechlorinated water (water ager/water conditioner or water dechlorinater) You don't need to buy an expensive one that might contain aloe, this will only add to the bioload in the tank. Sometimes as the saying goes less is more.
If any have fungus, don't treat them in the tank, remove them and give them saltbaths (even if it means staying up later) twice a day (nothing else). Empty saltbaths after each use (as fungus may drop off in water). Also the reason your white ones have pink tails - tank temperature (but can also be combined with the water problems you've been having). Ours are starting to get pink tails now as it heads towards 20C. We usually use that as a guide to keep an eye on all of them at the onset of summer, as it's a bit harder to spot on the dark wildtypes. Once they start floating or wobbling or develop fungus that is basically because their immune system has lowered, due to lack of tank maintenance and proper care or temperature.
To keep the tank temperature down, move to a cool area, if need be shut the curtains, surround the tank with polystyrene (sides and back).
Also, why are they using aniseed? Not sure what you mean by that.
Check out your local council as well for earthworms, most generally run a composting site and will be able to advise or even sell you worms. Otherwise another Aussie member mentioned they can be bought at Bunnings, sorry Lisa missed your post above
, so try any hardware or garden centres in your local area (by phone rather than visiting first - I realise distance to places over there is much greater compared to our NZ shops in some cases and not necessarily a 5 minute drive or walk down the road!)
If you're using the meat in foil packets sold at the petshop (I have a vague idea of what you mean), you'd be much better of just buying a cheap red meat (heart or snitzel or steak) and slice it into wormlike strips. Anything that is frozen needs to be thawed and rinsed before you add it to the tank (ie frozen bloodworm cube).