Hopefully, you quarantined them for the proper amount of time before introducing them into the aviary?
Quarantine means housing the new bird in a different cage in a different room than the current bird (as far away from the room the current bird is in as possible) for a period of 35-45 days.
Budgies mask symptoms when they are ill. Symptoms may not show up for over two weeks.
Often you will not even realize your bird is not well. Many budgie illnesses are airborne which is why you need to quarantine your new bird in a completely different room.
It is also a good idea to always take a new budgie in to see an Avian Vet for a "well-birdie" check-up. This allows you to develop a good relationship with the vet and the vet can establish a baseline for your bird in case of any future illnesses or injuries.
As you now have mixed genders in the same cage, it is imperative you do everything necessary to prevent breeding.
Rearranging their cage frequently, and limiting the light they get to 8 hours a day will help tremendously. Please be sure you never put a nest box or anything that could be used as a nesting site in their cage.
When they come into condition, limit the amount of protein in their diet at that time.
What little cuties! They’re all beautiful. But I’m not so sure they’re all females when I take a closer look. The blue one is a female for sure. The white is a male, and the yellow could very well be male too.
Please read the links above from Deborah (FaeryBee). They’re very important when keeping an aviary with mixed genders.