Quail are dying. Thoughts?

[Chicken_tiger_catt]

I’ve lost somewhere between three and five Japanese quail in the last month. None of them are laying eggs, despite all being mature. They eat the same layer food as my chickens. Because of that, I’m 90 percent sure it’s a nutrient deficiency. The symptoms are loss of balance, low or no egg production, trouble staying upright, and heads that look like they’re upside down. This has not impacted my chickens at all, despite them being housed very close to the quail enclosure.
Am I right? What are they missing? Is there a way to supplement it without buying the more expensive food?
(Pictures of me holding one up so it can eat. This is currently the only bird which is unwell, but I already lost one of its roommates. Its sibling appears healthy, but I know that they can hide illness, so I’m really not sure. Also note the nearly upside down head when it isn’t focused on food.

 

[kattabelly]

I don't know anything about quail but the upside-down head looks a lot like torticollis, aka wry neck. It can be congenital or due to injury or illness but can also caused by malnutrition. The treatment for a chicken would be to give a vitamin E capsule and a quarter of a vitamin B complex tablet, plus some scrambled egg for selenium, every day for a week or two. I'm not sure if people usually use the same or smaller doses for quail. Depending on the severity you might also need to feed them until they're able to eat themselves - there are a few ways to do that.

Can you post details of what feed they're on now? (Nutritional info, not just brand name)

@Nabiki is an educator and knows about quail, I think.

 

[Nabiki]

If they're eating chicken layer feed, they're definitely suffering from malnutrition, but the twisted neck has me worried. I strongly recommend getting one of the bodies tested. The twisted neck could be a sign of Virulent Newcastle's disease which is highly contagious and frequently lethal.

A necropsy shouldn't cost too much. You may see if a local vet can perform the test, and if not look up your state necropsy lab.
Edit: If it is Virulent Newcastle's, it can very easily spread to your chickens as well.