The seedling the blew over should be fine. Just keep some gentle air movement on it as that helps to strengthen the stalks. If your fan is too powerful when pointed right at them, turn it so the air hits the wall first, then the plants. As it grows more it should straighten itself back up.
If your seedlings are stretching too much, lower your light a bit. The space between the new set of leaves is called the node spacing. You want to have about 1" of space between the nodes. Just be careful that you don't get your light too low, as HPS lights are very hot and can harm the seedlings if too close. Place your hand at the top of the plants, palm down and hold it there for about 30 seconds. If it feels too hot on the back of your hand, it's too hot for the seedlings.