Answer: Spindly seedlings are usually caused by lack of light. (Since you have done this before, I assume you have thinned them suffciently and soon enough and have not provided them an excess of nitrogen.) If you are growing them in a sunny window, a simple spell of cloudy weather can cause the problem since sunny windows are usually only barely enough light in the first place. If you are growing them under lights, it's possible that you need to replace the bulbs. Also, if you are using the "miser" fluorescent bulbs they do have a reduced wattage significant enough to affect sun-loving plants in particular. Finally, be sure you are not overwatering and that there is sufficient air circulation to avoid fungal problems.
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