Bird's nest question

Unfortunately, that is a common appearance associated with stony corals in particular. That is the classic example of bleaching which unless the problem is addressed and corrected quickly, the coral will die. My guess is that it is a direct result of the placement of your coral and the lighting scheme as well. If your Seriatopora is receiving too much or too little light, this will be the most common result as your corals zooxanthellae is being expelled(brownish yellow/green color) thus showing its calcareous skeleton underneath.

It could be similar to montipora and Acropora, and could be possible for the tips to be just the iridophores and pigments associated with protecting the corals tissue from the harmful UV rays of the light from the sun or our artificial lights, similar to us using sunscreen!
But this amy or may not be the case here!
Try moving your coral to a different place! How close to your lights is you seriatopora(birds nest)?

 

Mine looks the same and has since I bought it and I have two of them.
The white tips are where the skeleton is being added to before new polyps
grow on it. The skeleton is almost white under the pink plops so far as I
know its normal.

Don't mean to disagree with you CR but here is a photo of mine when I first
bought it 2.5 months ago and its grown at least 1/2 to 3/4 of an inch since,
and as it grows the tips stay white. So I figure if it was a problem they both
would be dead by now.

 

I agree with gazog but there is one tip that looks like it might be losing some flesh.

 

Whew. Glad to hear that it's just a break

 

That was my main focal point, that piece on the left back branch!

 

Good eye CR