Well, the stock list is pretty high risk for peacocks to be involved, but with the ratios you are housing the auratus and zebras in, I can also see how they could be stressed. Both should be kept in larger groups, but I can't really advise you to add more with those peacocks in the tank. If you want to keep peacocks, your best bet is to go with the less aggressive mbuna, such as Yellow labs, Rusties and acei.
How large are the fish? Are they nearing sexual maturity? Have you had any breeding in the tank?
Once your tank is established, nitrates are very important to keep up with, so I would pick up a test kit for them. This is how you gauge how much and how often you need to do your water changes.
IMO, not eating and heavy breathing would be enough of an excuse for me to go ahead and treat for bloat. Once they stop eating, if it is bloat, it can be pretty hard to control.
You can do one of two things.
You can remove the fish that aren't eating and treat them in a hospital tank, and treat the main tank with medicated antiparasitic food.
Or, you can treat the main tank.
There are two treatment regimens detailed in the links below my signature.
I'm not sure what you have available to you in Australia medication wise, but you're going to need something for internal parasites.