It seems as if 6Dusters hasn't spent much time around tiny kittens. I can think of a million things that could be wrong with your kittens, and I know you know first-hand how sick kittens can be when the come into a shelter system.
It sounds like you're doing everything you can. I've had two litters so far this year that were on death's door, and it took a long time for the diarrhea to stop and for them to reliably eat wet and dry on their own. I agree that colostrum doesn't make sense for a group this "old." A few things I found that helped for the non-eaters:
1) Fluids twice a day every day, regardless of how they looked. Once they had 3 good days of eating, I stopped. If they have one good day and you stop, they tend to slide backwards (in my experience). I just thought about this today and thought I would start giving them to her 2 or 3 times a day until she was gaining weight and more lively, because you're absolutely right, she'll have a good day and be on the fluids and eat and I'll think "ok, she's alright, I wont stick her today" and then she's crappy the next day...so yes, fluids, fluids, fluids...life saving little fluids.
2) For the vomiting one Same kitty...she's puking and all of that...no one else is puking anymore., try a mixed of canned A/D, KMR, and a tiny bit of 100% pumpkin puree but make it pretty watery. Force feed tiny amounts (3mL or so) at a time and see if that stays down. This has been the winning thing for me with the vomiters. I'll pick some pumpkin up today...if I can make it over to work I'll pick up some A/D as well...if not, I'll bring it home tomorrow when I go to work.
3) What meds are they on? Depending on that, metronidozole has been a lifesaver (literally) for mine. It stops the diarrhea quickly, so they feel better, and consequently eat more. They are on Albon for the Coccidia and I just gave them all a dose of Strongid for worms if they have them...
4) If you have bottle babies that aren't eating solids but doing well on the bottle, keep them on the bottle. With the sickness they have, they need to keep hydrated and eating. You don't want to do anything to jeopardize it (I know you know this!). I always let babies work at things on their own terms, I offer them the other types of food, but if its the bottle they want, its what they get. Eventually they'll show interest in either the soft or hard food and I'll wean them off the bottle, but until then...I don't want to have to give fluids to anymore kittens!
5) You have to force feed any that aren't eating, or are only eating tiny bits. If you don't, you're almost guaranteed to lose them. That's what I've been doing with Bianca...the one with all the troubles. I just put some food in her mouth and she'll swallow some of it (Soft food) and I'll rinse it down with a little KMR 2nd step (nice and watered down so its not too thick). I always make sure she's at least putting a little bit of something in her tummy...even if it doesn't look like a whole lot.
I would not even consider letting these guys out for a least a week (preferably 2). Your profile says you have house pets, and the last thing you want is to get them sick too. Good luck! Absolutely right, no one comes out until they are better. I don't want any of my animals coming into contact with their feces. On top of that, I never let kittens roam until their litter box habits are about 99% perfect...I don't really prefer to shampoo up poopy spots...haha
