Bug eyed chicks

[Snozzle]

I have found a few other threads on this, but no real explanation of the cause.
My friend hatched these a few days ago and I took them with me since I have a peep ICU here and also am fascinated with genetics and mutations. They are from salmon Faverolles from the same bloodlines as mine, hatched in a similar incubator as mine, but I have never seen this before and 2 in 1 hatch at that. They are in a brooder with an older very sweet and gentle Sultan bantam that seems to be caring for them and they are getting high protein chick crumbles, electrolytes, probiotics and saline eyedrops, but they are very weak and I am not sure if they will make it, though they have been eating. What causes this deformity?

 

[dawg53]

Here's a link, post #4:
https://www.backyardchickens.com/t/555246/chick-with-bug-eyes

 

[Haunted55]

In humans, this type of a defect is caused by a lack of B vitamins, especially Folic Acid. I have never had Faverolles before so I am not familiar with them or if this information would even be pertinent here.

 

[Snozzle]

Should not be a deficiency since the parents are pretty much free range in my friends garden and are on the same food that I feed my birds too and I never have seen this in mine either. In humans I would say possible thyroid issue, but I am not sure about birds. I saw that link too, seems to be a Faverolles problem maybe? It's just so odd to have 2 in the same hatch and it's a breed that she, a few of our friends and I have been working with for a little while and none of us has ever seen this.