Abnormal stretching in the seedling phase is a sign of stress. By far, the most common situation that causes seedlings to stretch and topple over is light deprivation. In the same way, taproot digs for water and nutrients, the top part of the plant will stretch vigorously if it is not receiving enough light. So the light needs to be a little closer to prevent the stretching. Hopefully, I answered your question and remember Happy Growing and Free your mind one puff at a time.