Hmmmm, AGY without weight loss, regurgitation or anything, eh? That's a new one to me but it could well be that you caught it in its early stages (good for you!). It's very common in budgies, unfortunately.
I would eliminate all simple carbs especially all sugars (no bread, no juices, no fruits and check the vitamins label, if you give them any, because they sometime contain sugar) and would treat with thyme, oregano, barberry, garlic and Oregon grape. I would do them all except for the garlic as an infusion to add to his water, and add fresh or dried oregano and finely chopped garlic (just the tiniest bit, though) to his soft food (I have an oregano plant in my garden that it's supposed to be annual in the Northeast but, when it dies off in the winter, I cover it with mulch and it comes back every spring - I went to check it two days ago and the little leaves are already coming up from the soil). You can also get the oil which is more concentrated (make sure it's origanum vulgaris and not 'wild oregano' which is actually marjoram). I would also supplement with immune system boosters like Echinacea (only 5 days in a row and rest for 2), noni and DMG (oregano also boosts the immune system).





