I didn't have the answer either,so i found it for you.
It is a stress response when a healthy plant “reverts” back to 3-point leaves. Typically this happens when there are major changes in light quality or light schedule. For example, the following plants were switched from a fluorescent light to a powerful LED. A few days later, all the leaves were growing with only 3 points. In this case, there was nothing really “wrong” as much as different. The plants adjusted to the light and started growing regular leaves within a few weeks.
These plants started growing 3-point leaves after being switched from a weak fluorescent light to a strong LED