Stale Leaves and Stems???

My plant in the beginning of its seedling stage were doing just fine. In a few weeks the stems started to curl from heat stress so i lowered it. In a matter of hours the stem and leaves were so stale that they would crumble when tapped. What can i do to prevent this problem from happening next time? I was currently using two daylight cfl spiral bulbs 100watts equivalent to 27watts with 1300 lumen output each.