Okay it's good that you read the soil/fert bag, a lot of people will add fertilizers to that mix and burn the plants. A real quick, but only temporary fix would be to go to the nearest hardware store and buy a 42watt or higher compact flourecent or a circular flourescent tube to screw into that light socket. This will imediately improve the lighting and should stop the stretching, you will be able to get it closer, because the flouros put off a lot less heat, but it will still burn the leaves if it touchs directly. You must work fast, because those seedlings grow pretty quick as you have already seen. Once you have the lighting fixed for now, you will want to plan on an upgrade, because the larger the plants the more light they will need.