Hi Jen,
Please don’t beat yourself up if you do lose this little one, it is sad when you do lose one but you have to remember the others you have helped and focus on all the others that you are looking after.
Over the years at our cats4youinpattaya shelter we have lost many little ones who were just too small and weak to survive we tried our best for all of them though and never give up even if there is only a minimal chance of success.
Of course when they do make it, it is surely the most satisfying feeling you can ever have even after many weeks of feeding every 3 hours day and night !!
Have you tried changing the milk for the sickly one, we often use KMR but with our last rescue Baggy, she quickly got diarrhea so we changed her to goat’s milk which soon did the trick.
When kittens are very young they cannot regulate their own body temperature Strangely enough even here in Thailand small babies get cold very easily so we always keep them in a small basket with lamp to keep them warm, if they get too cold they quickly go downhill.
Only few weeks ago we tried to save 2 tiny premature babies who’s mum was killed in a car accident our vet performed a cesarean operation, 2 were already dead but these 2 survived, they were just so tiny and would not feed properly sadly we lost them both after just 2 days of struggling.
Good luck with your little ones and please let us know how you get on,
Keep up the good work,
Paul, Sandra and the cats !! .