Based on your specifications and set up I'd go Cfl....Especially if heat is gonna be an issue. Depending on what I'm growing and where I'm growing I use MH/HPS or CFLs. I usually change up depending on quantity of plants because a MH/HPS lamp will cover a larger area when compared by wattage...
That's why...lol. Too much fertilizer. How often do you water? You probably wanna flush her a couple times. I wouldn't recommend ferts more than once a week, because it will burn them.