I don’t like the idea of an enema for a kitten so you might give him a bit more mineral oil. Of course, if he needs it…
Since he seems a bit slower put a dab of Karo syrup or honey on his lips. That will give him an energy boost. You can give him that as needed and hopefully, he’ll get to move about some more.
Sometimes, parasites are hard on a kittens’ body. Check with vet. about when you can de-worm them.
Now this is a sad but, important, topic. Fading Kitten Syndrome (FKS) is not a disease. It is a collection of symptoms, the very first of which might be the unexplained death of a very young kitten. It has been compared to SIDS (Sudden Infant Death Syndrome) in human babies. It’s also called failure to thrive. It’s something that usually happens within the first two weeks of life. It can come from environmental factors, such as maternal neglect, or it can be physical, such as congenital birth defects, low birth weight, and anemia. Various infections also can play a role. FKS happens to the best caregivers.