Not enough water or not enough nutes.
think its nutes.. iits my first grow for nuting we were only mixing nutes into 1 gal of water, and plant is in a 5 gal pot..
should be using 5 gal of water right?
Well i do know train wreck is a popular breed that does not produce big buds but dense buds. If a light leak was your problem then you would most likely have a hermi on your hands.
I really dont think you did anything wrong. It may be a very good grow for ya man.