They make electrolytes for chickens to mix in the water. Have you used any electrolytes? I mixed it in my hens water when they were chicks. I would never had known about it, but a friend of my dad emphasized using it. Don't know what to do about them not eating.
Where did you get the chicks? Are they pooping? If they're pooping, then they're eating, they might just be shy about doing it when you're watching.
Also, you can see signs of dehydration in chicks by checking their legs. If their legs look full and filled out, then they are fine. If their little legs look dry and wrinkled and shrunken, then you have a problem.
The other thing to consider is, are you checking their vents to ensure they don't have pasted vents? That's where feces clogges their vents (the place out of which poop comes) and they can't eliminate. If they have pasted vents, they won't eat, because if there's no place for the poop to go, they're not hungry!