People are reading this, and it is important that no confusion remains, especially when dealing with the focal point of how to treat. So apologizing to
@Tycine1 I must mention that she meant miconazole(=antifungal) and not metronidazole(=antibiotic). The confusion arised because of the notorious article being posted. This one:
https://www.birdhealth.com.au/vent-gleet
Whenever this confusing article is being linked, it should always be explained that it is excellent in the first part and a total train-wreck in the second part. It goes off the rails by recommending 'blanket antibiotics'.
And now for something completely different (I'm afraid I'm betraying my age

).
When I read in the introductory post here
'I have given flubenvet back in early Jan as part of our normal 6 month de-worming regime' , my heart sank, because I'm of the 'less is more philosophy', and the OP was asking direct questions about something else, and really... why open a can of worms? But now that this can of worms has been opened... Routine worming is a matter of personal choice for every owner and here is why I don't routinely worm:
1. I trust their immune system to protect them and make sure I support it with nutrition, the elimination of stress and cleanliness.
2. I want to 'keep my powder dry' for when I really need it and am worried about creating anthelmintic resistance.
3. Side effects. I looked up Flubenvet = flubendazole = similar molecular structure to fenbendazole (Panacur). PoultryDVM says about fenbendazole, rather cryptically, ' toxicity has been reported, particularly in birds.' Well, it's liver toxicity, and who wants that?