Taxman, I ran 400w 65k iwasaki's over a year, several years back. Basically the only reason I got rid of them was the heat they put off and my chiller couldn't keep up. During that time I had some of the best growth and coloration I've ever had in my acropora collection. I opted to go back to the 250w iwasaki's. I was able to raise my canopy and lower it to acclimate my corals. This was on a 120g with 2 lights. I know that several of my sps friends have had 400w iwasaki's but most have also switched to some sort of 10k now. Myself included.{Thanks to Jim Norris}. I also run carbon 24/7 and just started using ROWAphos too.

I don't think your temp is bad but I wouldn't let it get any higher. I keep mine at 77-78. I think I have to agree with the ideas your lights may be too low. I literally burned my arm working in that tank when I had the 400w iwasaki's on it. If it could burn my arm I'd hate to think what they can do to corals.