same thing happened to me i have them on 24/7 light and 4 CLFs in desk lamps in each corner, when i added a 2' long FL about 2" above the week-old seedlings, 3/4 died! i think they got burnt, weird thing is one seedling didnt seem to suffer at all, it was bigger than the others and maybe survived the heat stress better. i turned the long FL off.... hoping #4 stays healthy.