Usually, leggy means they need more light or light of a higher intensity. If they're in seed flats you might try placing them outside during the day (put them in the shade out of direct sunshine for the first week). If they are outside and in seed flats you need to move them to a full sun spot in the garden (check them in the middle of the day to make sure they aren't wilting). If they are in the ground (direct sown) then something is blocking the light. If that something is not moveable then I would just wait, they usually over come the legginess once they start growing real leaves. If they can't get enough light, they may always be leggy and stretched.

At my old garden, which only had 6 hours of full sun in June, my tomatoes and peppers were often head high before they bloomed - there just wasn't enough light no matter how "sunny" it looked to me.