We are not avian vets here and I cannot advise you on medications.
I suggest you telephone your vet or contact an online vet and ask their advice for the meantime.
Your bird may have an infection, but also may just be settling in to a new environment, and there are side effects from (possibly unnecessary) antibiotics to consider. If sheís eating & drinking well, then Iíd likely just keep a close eye on her, and if sheís not deteriorating, wait until Monday.
Is it possible for you to separate the two new birds from each other?
Are those medications left over from previous treatments? If they are not unopened and within their use by dates, then I would not consider using them. If they are new, then what was the reason you purchased them?
When you meet your vet on Monday, it may be useful to ask whether they feel that having antibiotics at home is a good idea, and what degree of what symptoms would warrant their use.
Best of luck.