Unidentified Quail Chick Beak Disease?

[cdng]

I just picked up 10 coturnix quail chicks yesterday, and this is my first experience with keeping them.
My sister picked one up today and was concerned about its beak being pliable, "rough" looking and of dark colouration . I am attaching a picture of the most affected bird, a few of the rest just have a dark "spot" or two on the edges of their beaks. I looked for info online and the only thing I really know is "might be fungal".
Here is more info about them
Chicks are between 3 and 5 days old.
They are seemingly eating, drinking, and pooping with ease.
The insides of their mouths look normal, but the beak is kinda "soft".
I have ACV added to their water at one tablespoon per cup of water.
I just used a swab to rub ACV on the affected birds beaks.
I also put a mixture of raw cinnamon honey, 1 drop of oregano oil, and a probiotic capsule directly on the beak.

So has anyone seen this before whether on chickens, quail or other birds or know what else to do?

 

[Eggcessive]

I have no experience with quail, but in the second picture, the dark matter looks a bit like canker, a protozoan infection, which is contagious and carried by pigeons. I would quarantine these chicks, and contact the seller. Hopefully other quail people will see this thread and respond. I would also recommend posting on the quail forum. It is under forums, then scroll down to "other backyard poultry." Welcome to BYC.

 

[cdng]

I looked it up and I don't think it's canker as there is nothing in the mouth only on the outside of the beak.

 

[cdng]

The weird stuff fell off today and I realized what it was, EGG YOLK MIXED WITH DUST! I fed yolks to them yesterday and offered them a dust bath. So I feel like a noob(then again no matter how much I've read about them I am one.), but I'm mostly happy that they are fine.