Hello...
Seen these scenerios all too many times...been some good advice tips so far IMO...
#1. As stated those 400 DE are BLEACHING bright unless like 18 plus inches above the water, and on a 4-8 hour light cycle...if they are Hamiltons, thats the cause there I bet...hammys arn't impressive bulbs IME....terrible....
#2. yes PO4 can cause the brown...but these corals are white...this man would love to have deep brown shaded corals instead of extremely thin skinned white corals, that are near dead as we speak...
#3. I use Radiums (250 SE x9 hours), with ATI G-manmn T-5 blue pluses (x3 12 hours)with a short 5 hours of x2 URI aquasun VHO's (brings out the purples and pinks) over my 180 acro tank for example and have the richest deepest colors I've ever imagined....I have near 20 fish in there including 5 large tangs..I feed VERY heavily x2 times per day...literally a handfull of frozen food per day...thats how I get deeper colors is heavy feeding...but one must be able to process that added food...I use a few things not least of which is a DSB..(I'm not anti-BB...LOL)
#4. IME when my ALK gets that high as yours (11Dkh)...I lost mega color...goes below 7 and lose color and PE...my alk is best at 8-9 tops...Alk has a MAJOR part in sps coloration...at least proven to me by my relentless experiments here at my make-shift labratory/frag farm...
#5. The legendary red bugs can have this prolonged effect on only acroporas
#6. MOST IMPORTANT....This is one of the most overlooked things...probably because its so simple....I had problems for years and years as a younger reefer....wanted better color from my sps...and would lose PE on a colony hit and miss followed by STN/RTN death...tried EVERYTHING...well almost everything....its those dirty stinky no good handheld salt meters (hydrometers)...they are BUNK!!!!!!!!!!!!!!!! The makers of these so called instruments must know this....they are killing hobbiests dreams and corals by the thousands...I had a high quality handheld hydrometer, my brother had one, my cousin had one...every reefer around here had one (probably because I did and I had gotton them all started in the hobby)...all the meters when compared to a real salinity tester (
REFRACTOMETER), was reading .031-.035....I near fainted upon my discovery of this...corerected the problem (refractometere reading of a steady .025)...had intense sps color for years now....
BIGGEST TIP I can ever give to reefers...
BUY A GOOD REFRACTOMETER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!....its the most important instrument you can have for reefing!
Hope my nickle advice helps..
Doc