most of my corals getting brown

[redadeath]

my temp is
30 degree celcius

ph 8.1
kh 10
calcium 400
magnesium 1250
nitrate 0
phosphate 0
i have some cyano problem

i dont know what is the main reason that my corals get brown

i run 250 metalhalide hamilton tec * 2

all parameters are good

i also acclimate corals for light

i only run my metalhalide for 5 hours is that enough??

can any body tell me the main reaon for getting brown 3 days after adding it to aquarium

 

[redadeath]

need comment plz

 

[seafd]

Well the temp is high, try 23-25 degree C. I would use a fan to get some additional evaporation to cool the tank down, or a chiller. You also may need to leave the light on longer, try 8-9 hrs. Watch that the additional lighting time doesn't increase the tank temperature higher than it already is.