I hope it is not going to be a problem for your crotons. I would not have even realized there was anything wrong with them, just would have assumed that was the color they are supposed to be. Good luck figuring out your mystery. It was a colder than usual winter at times here, so don't know if that can impact anything. I noticed that many of the crotons took a beating at Harry Leu Gardens in Orlando, some being killed back to the ground. I lost a few really sensitive plants but most things are really looking good with the recent rain. Unfortunately that includes the weeds.