Light Bleaching Acro

[Opah]

Acro frag started bleaching. It's fairly close to the MH bulb (~12"). Lighting is 4 x t5 + 2 x 400W MH 20k. Par is ~400. Other across and sps are doing fine. I had tried to acclimate with frag rack, but could only get up to 250 par. I did ramp up the lights by about 30 minutes a day until it MH were on for 8 hours. I'm planning on reducing the duration of the MH from 8 hours to 1 hour on -> 15 min off -> 1 hour on and ramp up. Any advice?

Parameters
salinity 35 ppt
alk 8.6
ph 8.3
mag 1395
calcium 450
nitrate 3 ppm
phosphate 0.017289 mg/l
System is 11 years old

 

[Opah]

Other acro and sps