Lighting?

I have been adding a few corals to my system and am getting more concerned about my lighting. What is ideal? I know that it depends on a lot of different factors, like the types of corals, depth of water, etc. I also realize metal halide would probably be ideal, and I am seriously considering adding that to my system too. Again, what wattage and temperature is best for that?
Anyhow, I currently have a 135gal DT (72" long x 24" tall x 18" deep). I am using one 72" Coralife PC fixture with 4 96w 2-in-1 (Super Actinic/75-25) bulbs. The 75-25 half is supposed to combine 75% super actinic properties with 25% daylight properties producing a 14000K color temperature. The super actinic half is supposed to peak at 420nm. I also use a 48" T-5 fixture with 4-54w 12000k bulbs in it. I get a very blue color to my tank and it looks really nice, although I had hoped it wouldn't be so blue when I picked out the bulbs.
 
I am considering taking the T-5 fixture out and replacing it with 3 150w metal halides. If I do this, what color temp should I look for, will it be worth the exchange, or are my current lights good enough? Also, if my current lights are good enough, should I have a different combination than what I am running?
Something just seems off on my system and I can't pinpoint it. The parameters are all perfect, I don't have any hair algea nor do I have any red slime...although I do have a little bit of a blanket of algea on the sand bed. My coraline purple is spreading wonderfully and most of my corals seem to be doing well. Although, I have attempted to add red caps to my system a couple of times and they die almost immediately. I also have a GSP that isn't doing well, it seems to be dying off rather than growing. My small xenias are growing at an extremely slow rate and the larger ones I put in were all eaten by my perppermint shrimp. The only thing I don't have a test for is magnesium, but I add some once in a while. 
I am worried that my lighting is my problem at this point and would appreciate any advice that anyone could offer. 
Will