Advice Welcome

Use seed starter soil.... not MG flowring soil

Ok, I have a some widow plants. they are around 3 inches tall. I have killed 3 plants in 4 days. Now 1 has dark brown spots around the edges. but looks fine. should i worry? and any suggestions about not killing so many plants? i germ them until there bout a half inch long. then put them in jiffy seed starter soil and the other in plain hyponex soil. i have 6 23W cfl 6500k lights on 6 plants all under 4 inches tall. The lights are around 5 inches away from the plant. Im watering every time the soil is all the way dry.