got some good growth, would help if you changed to 10k bulbs or blv14k.
As i have noticed heaps of growth with brighter bulbs,
The narva 14k look very nice but not good for coral growth.
I read somewhere that adding to much amino acids causes the brown diatoms. i am getting more diatoms when i stated to dose Salifert amino acids. Higher temp also causes the diatoms
I think you stated that you had 0 Nitrates, I have found if you can increase your nitrates your will get better colours.
raised mine from 0 to 2ppm and overnight i noticed better colours.