Eyeworms are difficult to get rid of. Their eggs will contaminate the soil and you'll end up tracking the eggs into your chicken pens and will be picked up by your existing flock.As an update to this I found Mason's eye worms in the eyes of the smaller chick this morning. Judging from all their symptoms I think fowl pox + eye worms explains everything. I pulled out two worms by hand but I can't get the rest so I'm going on a quest for Oxyrid tonight.
The chicks are quarantined from my other birds and I'm practicing good quarantine hygiene.
I'm sure your culling advice is very good for anyone in a similar situation but I have no intention of adding new chicks to my flock, and since there are so many feral birds around it seems like whatever illnesses are going around will just be in the neighboring feral flocks anyway so culling won't make a difference. Plus if it's just eye worms + pox these lil dudes should recover and be fine later.
Thanks for your concern and for your answers.
Oxyrid will not prevent nor treat unseen worm eggs. Cull.