looking for advice

I have 180 gallon reef tank, that has been operating now for about six months. I recdently upgrade from a 150 gallon tank that I had opearting for a few years. In the previous tank I had no issues keeping corals.

The set up that I have is as follows: six T5 54w bulbs..2 white , 2 blue, 2 pink, on for aprox. 10 -11 per day on timers. My lghts are sitting on top of my tank about six inches from my glass. The lights are 48 inches( the tank lenght is 72, but I have my rock set up so corals are directly beneath the lighting system, and that I have less direct light on either end, where my anenomes seem be to happy. Sump system with skimmer in sump. 4 water fans plug into an " ocean pulse " wave maker. 2 pumps position on back of tank, and two more position on either end. Due 10% water changes once a week. Specific gravity at 1.025. Have an RO water system set up for my water changes and top off.


Currently in the tank, fish, tree corals, leathers(soft), carpet and bulble tip anenome that are doing fine. I can't seem to keep hard corals. usually dye withn the week. Also micro feed, turning skimmer off for a couple of hours. Supplements such as calcium levels etc. are checked on a weekly basis. Keep my calcium levels at around 420 - 450.
I had this same set up when I had my 150 tank, and my corals flourished.
I was thinking of going to a combination metal hallide T5 set up 72 inches.

Any thoughts.