I’m really sorry to hear about your kittens, I know how hard it is to see them in such distress. The suggestions the other made are good and, unfortunately there’s not a lot more you can do. I asked the vet at the shelter where I work, and URIs (upper respiratory infections) are really tough to deal with. Nearly all the animals we have, have it. If that’s what they have, it’ll just have to run its course. All I can further suggest is to keep them warm and comfortable and let them get as much rest as they can; whatever it takes to keep their immune systems up. I hope they get better soon and I’ll keep them and your family in my prayers.