Birdsnest problem

Hi there everyone.

I'm a new member to 3 reef and looking for a little help and advice. I'm having a problem with my pink birdsnest coral. The tops of a couple of branches seem as if it's starting to bleach, the bottoms of the same branches appear to be fine with full color and polyps. This has been my fastest growing coral and no changes of placement have been made. As far as water parameters go, calcium is steady between 430-450, magnesium 1300, dkh 8-9, phosphates 0.00, nitrates 0-10, salinity 1.025. My calcium and phosphates is a measured off Hanna checker, the rest is measured by salifert. My lighting is 2 ecotech marine radions on a 75 gallon tank. The birdsnest is placed a little above halfway point almost in the center. So I guess the question is, what could I try to save this coral as it is one of my favorites? Thanks in advance for all the help and advice