Sorry to say I'm not experienced enough to help you, but can you tell us more about his symptoms and his living situation? That will help someone here with more experience to figure out what's going on.
Is he eating? Drinking?
Is he pooping a lot or? Still looking runny?
Wings drooping?
Walking around or lying still?
Doing anything unusual with beak (for example, open, "gaping" like a baby bird)?
Having any trouble with breathing?
Eyes drooping or normal?
Have you had any sudden weather changes?
Is he in contact with chickens or other poultry?
Could he have eaten anything toxic?
She died this afternoon, but so that I may know how to address this in the future, I'd like to step through this in the event the other 3 are sick.
I got to her late, and immediately started electrolytes and water.
She had runny yellowish poop.
Wings were drooped.
Laying down.
Gaping every 30-45 seconds.
Distressed breathing.
Pupils were dilated severely, and her eyes were listless, and she wasn't wanting to open them.
Weather in Phoenix has gotten chilly at night.
They are living and free ranging with the chickens until our big coop is built for them. We are planning on separating them.
It's possible, but unlikely that she ate something toxic. They free range, but we don't have a lot of critters running around right now.
@Glenmar, thanks. After looking into it, is going from healthy to dead in under 24 hours consistent with a parasite/worm?
If anyone knows a breeder here in Phx that I can get a few more from once we figure out what we've got and how to deal with it, and the new coop is finished, it would be appreciated.