We are fostering a female and her 7 kittens. One of them since 6:00 am to 8:00 p.m. has gone down hill fast, and no vets are open in our little town. The kitten is lethargic, mostly non responsive, but will occasionally fight when we try and get liquid into it. You can barely feel the ribs, but the spine and hips are very pronounced. The skin reacts as though the kitten is dehydrated, yet it refuses water or kitten milk replacer. The female doesn't nurse them much, but the rest are eating some dry food. Also it's equilibrium is almost completely gone. It was not like this this morning, and it's siblings are very active and alert.

If it won't take warm milk or melted warm ice cream from an eye dropper you just have to let it go. Not every kitten is going to make it - have seen that over the years. Like human infants sometimes birth defects show up very early and the kitten's system will just shut down, like Sudden Infant Death Syndrome.
Sounds like you've done everything you can.
The only other thing you can do is some energy healing - hold the kitten in your hands over your heart or belly button to give it some life energy. However, dehydration is just the end for cats so I think it's just too late for anything at this point.

Some of God's critters are only here for just a little while, others for longer.

We are fostering a female and her 7 kittens. One of them since 6:00 am to 8:00 p.m. has gone down hill fast, and no vets are open in our little town. The kitten is lethargic, mostly non responsive, but will occasionally fight when we try and get liquid into it. You can barely feel the ribs, but the spine and hips are very pronounced. The skin reacts as though the kitten is dehydrated, yet it refuses water or kitten milk replacer. the female doesn't nurse them much, but the rest are eating some dry food. Also it's equilibrium is almost completely gone. It was not like this this morning, and it's siblings are very active and alert.
Thanks anyway, but the kitten passed. The vet I took it too said that it faded, which isn't uncommon in large litters.