Trumpet coral partly dying

[Carl C]

I’ve had this coral for a while, suddenly some polyps are turning white
Any ideas ? Normal ?

Haven’t changed lighting

Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate: 8 ppm
pH: 8.2
Specific Gravity 1.025
Alkalinity: 8
Phosphate: .10 ppm
Calcium: 430
Magnesium: 1310

 

[jordan10]

Flow hitting to hard? Pic might help. Numbers look good