Hi there sending healing vibes your way
You could also
try SITZ BATHS! (I'm NOT kidding).
You have the room nice and warm of course.
You have a little bowl or whatever the kitten will fit in
nicely, put nice warm not hot water in the bowl.
Then, for 2-5 minutes, you hold the kitten so its abdomen &
bottom are in the nice warm water.
Kitty will scream bloody murder! It's hard to hold the kitty
in there. Piteous mews! I sang to them, they were still upset!
Then of course dry well, warm up, cuddle, listen to them
threatening to call the Cat Abuse Hotline.
We did this on a 2 week old (who fit in a tea mug w/water),
and on a bigger kit in a soup bowl, or other type of container
You need to do this at least twice a day.
We usually saw some loosening up in a day.
I had to do this a few time over the years and I have done it with bigger cats as well, if you have a second person on hand it helps as there will be a bit of a struggle with kitty
I think its worth a shot for colby you have nothing to lose and everything to gain