How long have you had these corals for ?
1000 liters = 264 gallons [US]
Your Water circulation is around 18 X it should be more like 30x + That wont be cheap to fix.
Your dkh is balanced just a bit lower than most people leave it at I'd say shoot for 9.( Don't add to much at once do it slowly over 2-3 days )
(
http://home.comcast.net/~jdieck1/chemcalc.html)
Placing the coarls so that there is not Direct flow blowing straight at them yet making a strong current alternating if possable in there area may help.
200 Liters plus 20% of your sump and or refegium volume changed every 2 weeks is an average water change in good conditions in your case it should be more.
More bigger water changes like 35 % total volume. one or two phosphate reactor's ( two little fishies) And more water circulation.
Now lastly if those lights were right above the coarls it might help. I think a 250 watt Double ended pendant right above them would do better ( I have the same corals with this lighting above them and growwing) It's the intensity of halides thats better T-5's or vho may work depending or water clarity and the distance from the light !
See this link to see what someone with one of the best tanks out there uses for his 1150L tank wich is not all that much smaller than yours .
http://www.reefkeeping.com/issues/2008-05/totm/index.php
This is his circulation ( its at 156 X ) to give you an idea you dont have to have this much but it shows that a tank like yours could benefit from allot more flow ( my 750 Liter tank /sump is at 43X I have only 8 fish )
- Tunze Wavebox 6212 x 4
- Tunze Turbelle Stream 6301 x 2 (side position)
- Tunze Turbelle Stream 6201 x 2 (back position)
- Tunze Multicontroller 7095
I love the type of corals you have . I've got some myself.
I recently decided to try lowering my salinity to 1.021 to see how it affected things as I always seem to buy corals from stores with lower salinity. well I now have some white coarls and due to wet skimming I had gone to1.020 ( Ouch) I gradually brought it back up and the remaining living coarls are finally coming back to life !!
Everyone has struggles in this hoby no matter how much equipment or experience ya got !!!
Good luck
Paul