well there could be a few reasons as to why they died, it could of been you watered to much, your soil was to strong and burned them. or you used the wrong kind of light
you put them into to big of pots which could contribute to overwatering
you want to start them out in cups
also the bagseed you was growing could be bad genes, so there are more ways to as to why they could have died
what soil are you using and what lighting was you using and how often was you watering and what did you have the seedlings in?
this is what you should do
start out by getting a seed starter soil mixture
take a rag and put some seeds in the rag and make sure the rag stays wet, to help soften the beans up
after you see them pop open take a pair of tweezers gently place it in the soil and put a little on the top
after the seed poped out you want to get some compact fluros or some fluro tubes, if you use fluro tubes you need the light to be as close as possible like 1/2 an in above the seedling
compact fluors do not keep them that close, the compact produce more heat
stay away from incadesant bulbs, they are not the proper light for growing and produces way to much heat
when the seedlings get to big for cups you will need to transplant the into a pot, i would say 1 gallon size pot and then when you flower i would move it up to 2 or 3 depending on the size
12 in tall plants per gallon size pot is the rule i follow
doing just pluck them into big pots, it wastes time and also causes slow growth in your plant
if your looking for something, take smokin alot's advice, lowryder is a small strain but it auto flowers, meaning that you dont have to put it into 12/12 lighting to make it flower
it can flower in 18/6
when you have seedlings for the first 2 weeks you want to keep the light on 24 hours
after 2 weeks you can wean them to 20/4 an then after that 18/6 and then 12/12
you dont have to go by that but i do, gives the plant a more sense of as if its growing outdoors like the lighting outside is getting les and less and means its time to flower
hope that helps you get a good jump on things, if you need to know more feel free to ask anytime