Coral Bleaching and Flatworms

Hey guys, I've been having trouble with corals in my 65 gallon display tank. The tank has been set up for about 10 months, although the system is going on 3 years since it has been upgraded several times. The problem that I'm having is that nearly all the corals in the tank are experiencing bleaching, and I've lost several nice pieces to bleaching and tissue necrosis. I originally suspected my custom LED lighting over the tank, and turned it down considerably to see if any of the corals would regain their color, but after a month none of them did, so I decided to turn the lighting back up, and so far there hasn't been any noticeable worsening of the condition of the corals. I'm sick and tired of dealing with this because I really want to add some more corals to the tank, but I won't add anything until I get to the bottom of this bleaching. I've tried and thought of everything that could have caused it, and I'm kinda stumped now, so I figured someone here would probably think of something I had missed or overlooked. Here are the tank stats:



65 Gallon Main display with 20 Gallon Sump and 20 Gallon Frag Tank

Custom LED's over the Main Display

4 t%'s over the Frag Tank

Flow: mag7 to main display and mag3 to frag tank

3 Koralia powerheads in main display

Filtration: Eshops psk150 plus weekly detritus siphoning from frag tank and sump

Chemistry: Nitrite:0

Nitrate:20-30ppm

Ammonia:0

pH: 7.8

Alk: 6dkh

Phosphate: 2ppm

Calcium:410ppm

Livestock: Pair of Occelaris Clowns

Diamond Watchman Goby

Red Head Fairy Wrasse

Yellow Candy Hogfish

Scopas Tang

Cleaner Goby pair



So yeah, I'm kinda stumped as to what it could be. The system has always had higher nitrates since it's primarily soft and lps corals, and I never have had a problem with it as of yet. Lights are on for 8 hours a day, so I don't think the photoperiod is too long. The weirdest thing is certain corals in the frag tank seem unaffected, while others bleached considerably, so I'm just trying to figure out to what to do. If anyone has any idea what could be going on please say, I probably left out some info so if you need more just say so. Thanks for any help!!!



Oh yeah, I forgot to add this, does anybody have any experience with smaller flatworms? I'm not talking about red planaria, I'm talking about dark red/black flatworms that are so small I can barely see them with my naked eye. I had a zoa frag that was closed for a few days, so I inspected it and found them. Checked a few other plugs, and discovered all my plugs had them. Maybe this could be causing some of the bleaching? I don't know, just thought I would add that in there.