How old is the chick?
If less than 24 hrs wait and see, as curled toes often resolve if the chicks are kept on a towl (or other good gripping surface).
If more than 24 hrs you can make a "boot" ie spread the toes out and tape them on to some light card.
Best results usually come if this is...
Technically speaking a "mixed color Ameraucana" (even if created by breeding 2 pure bred different color parents) is technically an Easter Egger. However many hatcheries, feed stores and even lots of "back yard breeders" call these birds Ameraucana. There is an Ameraucana breeders thread on BYC...
How about a basic how to incubate eggs video for total nubies, including which orientation to set an egg, temperature humidity, turning etc etc. Some of the newer incubators come with instructions like set humidity to 65% for the whole incubation period (this may be a translation issue)
And may...
I would suggest wet chick starter and (gently) push its beak into it so it knows where to find it.
I would also give it a buddy chick who will teach it without competition. If it does not make it don't feel bad-some chicks are just not meant to make it and you did your best.
How much vinegar is in their water?
They may just be a skinny breed. From what you describe (except maybe the ACV) they should be well fed!
Also are you putting anything else in the water like electrolytes?
I knew someone whose chicks kept dying because they were dumping tons of water...
I hatched out some Trader Joe fertile eating eggs. The birds are white and lay huge white eggs daily. They look a lot like leghorns (maybe a bit fuller in the body) but are not flighty like leghorns I have had before. Pretty sure they have some leghorn in them but what else i don't know. These...
I had peafowl and loved them. I knew I had to keep them (3) penned so that they would not damage neighbors' (or our) property. In the end I rehomed 2 of them them as IMO I could not provide them all with enough space. That was my choice, and it was determined by not wanting to detrimentally...