What's the cause of pale/bald on tip of SPS??

[Haacheew]

As you can see, the attached photos. What's the cause of pale tip on my sps. The white stem keeps growing longer without color, besides whtish, or polyps. My other sps are doing fine. Is it too much light for that species? All the common water chemistry are within parameters.

 

[ChuneReef]

Could you post parameters? In particular, Alkalinity?

 

[reefman888]

Look like growth tips

 

[Terry Le]

look like new growth tip to me