Water
Crotons need to have their soil evenly moist at all times, they tend to wilt easily if the soil is too dry. On the other hand if the soil is too wet the leaves will turn brown on the edges.
These plants also prefer to have a location with higher humidity. It is generally recommended that they be placed somewhere with a humidity of 40-80%. If the humidity isn’t high enough the plants will drop some of their leaves and the color of the leaves may not be as vibrant.