when you replanted it did you make sure the soil was nice and firm around the roots? Leaving the soil loose around the roots cause air pockets and will hold water and also bad for the roots. I have killed a many plants shortly after replanting them and I found out that was the reason for it.
I ask because a croton is pretty hardy plant, they can take a good amount of water and lo or alot of light either case they will usually hang in there.