The strain is not stable. If you are seeing a difference in the same seed then it is not yet stable. Take cuttings from the one you like best and clone. Some times I have to do that with cheaper non fem seed. I grew orange bud fem from Dutch Passion and the were all the same like clones. As to will they fatten up. Maybe if you take them long enough. You have to get a scope and check trichomes. Almost all cloudy is what you want. The one displaying sativa traits may take weeks longer.