What growing medium are you using... just regular dirt? I would suggest getting a medium that doesn't hold as much water. Regular dirt doesn't seem to work well unless it is fortified or built up a little. If the soil is too wet, the roots can't get the oxygen that they need to grow and thrive. If the roots can't flourish, especially at the beginning, the plant won't grow much.
I use Promix, which holds just the right amount of water. If you are having trouble, I would recommend somethin like Promix since it is very forgiving and unlikely to have problems unless you overfeed things. Promix is treated to keep the Ph near 7, so lockouts aren't likely. Sunlight is great, but you will need a lot of it to get a decent plant. Plants grown in anything but full sun don't grow as well.