Is it possible my light is destroying my tank?

[Reefingmark]

A couple months ago I purchased a cheaply made 48" t5/halide combo for my 75 gallon. Since then my tank has slowly went down. I'm losing coral and coraline algae. The only thing that seems to be surviving is my montipora. It seems the system was doing better on a 4 bulb HO t5 fixture.

The system is fairly new running 6 months old maybe.

Water Parameters: All my water parameters are good Nitrate:0 Nitrite:0 Ammonia:0 PH 7.6 Calcium: 450 or so Mg 1400 Kh 9.1 Temp 75-78 degrees

I was doing regular 10% weekly water changes before getting discouraged. I change my socks and clean my skimmer cup regularly.

But back to light. I am running a Oddysea halide 250w/T5 54w HO combo. I run the 4 Blue Actinics 8 hours and 2 15k halides 5 hours a day.

2x External Quick Connect 250W Electronic HQI Metal Halide Ballast
2x Internal Twin Output T5 Electronic Ballast
4x Power Switch on Fixture (2 for T5, 1 for LED, and 1 for Cooling Fan)
1x Power Switch on each HQI Ballast
3x Power Cord (2 for HQI and 1 for T5)
Non-Corrosive Powder Coated Aluminum Housing
2x Built In Heavy Duty Cooling Fan

http://www.aquatraders.com/48-716W-Metal-Halide-T5-LED-Combo-p/54267.htm

My question is whats going on with my tank?
Any and all help is greatly appreciated.

 

[boogie01]

Corals always seem to take a little time adapting to new lighting, maybe that's the issue maybe not. What are your tank dimensions? If it's shallow maybe the 250w mh is too strong

 

[d2mini]

What exactly is happening to your coral and what kind of coral?
Tank dims?
What is the range of your PH? 7.6 is starting to get a bit low.
And your Temp is on the low side at 75. Shouldn't matter much but worth mentioning.

6 months is just a baby and the MH are pretty strong. Did you go through any acclimation process?