White tips on duncan

[igadget56]

I have a 125 gallon tank. It is 18"from the surface to the substrate. I have two evolution LED's, the brightest that they make. The white lights are 20,000K. I have a par meter, I get 180 on the substrate. I have a large duncan about 15 heads or more,on the substrate. Why are some tips turning white? Below are just some of the other corals I have, some doing ok, most are doing great. I have a small duncan close to the surface and it is doing good. I'm running BIO pellets and phosban 40gl sump.

PH 8.0 8.1
Cal 460
Alk 8.7
Mag 1400

I am dosing 100ml per day of 2 part recipe 1. .
Candy canes
frog spawn
hammer
dragon soul
war cora
lobophyllia
chalice and a few more.

 

[Proseph]

Pictures always help