Seriatopora caliendrum under T5's

[exonn]

I have 72 litters (60-30-40h) nano, and want to keep some SPS, for now i have 3 24w t5's. ATI blue+, actinic and coral+. In a few days i'll put 2 more t5's. Thinking about 2 more blue+ (actuali osram e67). I have seriatopora caliendrum. I get it from a friend but in a really bad condition, it was all white because of LED's. After few months in my tank it looks better, polyps are extended, but the color doesn't look good. Its not all white, but slightly brown and polyps are vivid green only on a tips. I had some issues with my water parameters (low KH) but now everyting is OK. Is it possible that my seriatopora doesn't look good because of low light? It’s in a top half of a tank. For a flow i use tunze nano stream 6015. Other parameters:
KH 9
Ca 420
Mg 1300
Po4 0
No3 0
Temp 25 c
Density 1,0235

Any suggestions on lightening?

 

[stevedola]

3 bulbs is kind of weak. Is it high in the tank? I would definitely add 2-3 more bulbs for future SPS additions.
and yes, low light will lead to brown corals.

 

[exonn]

Thanks, will add 2 more t5 tomorrow... Hope it helps

it looks like thi now...

 

[stevedola]

no show

 

[exonn]

if you cant see the picture above,am attaching it.