New Zealand fails to grow - midget?

Question
I have a New Zealand white that recently had a nice healthy litter.  I noticed one bunny baby seems to have stopped growing but eats and plays just fine.  At first I thought it was a midget, but then someone told me it is something called coxi or cocci and if I don't treat the area, then I will start getting more midget bunny babies.  This "Little One" as we call him is currently living comfortably in a parakeet cage.  He is about three times smaller than his siblings who are about 5 - 6 weeks old.  His fur isn't quite as smooth and lush but he is fluffy and otherwise happy.  Do you know what exactly the disorder is, and what I need to use to treat the rest of the rabbit area with?  I have other New Zealand whites and don't want it to spread.  Thanks!

Answer
Hello Alannah

Congrats on your litter for bunnies.

I have never heard of this disorder before so afraid i cant be much help. If the bunny seems happy and healthy then i shouldn't think it should be worrying about. Go and see your vet just incase,  about this as they will be able to tell you the disorder, if there is one.

sarah