Update. 2 weeks ago I had a flock wide outbreak again. Seemed to have started in the budgies, which previously my vet said were the hardest to clear.
The budgies had some nasal discharge and poop change. The rest had weight loss of 5% on average with penny 8% all were given a short 10 day pulse of doxy. All bounced back quickly.
Except my old girl Penny . At first she gained back weight. But on day 7 started loosing weight again, and started regurgitate. She had developed yeast overgrowth and regurgitation. She is on nyststin and switched to a 10 day ( but only 5 treatments, as is every other day) azithromycin. Nearly finished and is doing good. Did have to start back formula support for her. Gaining weight, no more regurgitation. Whew @
You all thought , like me this was over@!@ but...now under vet advice will treat with a pulse every six months......sigh
The flock had been molting, and that little bit of extra stress on their bodies probably linked with the flare up. They are done molting now. Except Penny who's molting us prolonged from being sick. That's a tip off for your birds as well, a prolonged molting can point to a hidden health issues. As molting takes extra energy and calories, if also health issues they can't handle the drain. Usually I bump calories and protein before a molt but this one happened sooner than I expected...
I push again the importance of weight checks weekly. It only took a week for them to have weight loss. With zero other symptoms ( except budgies) eating, active, poops normal.