one plant flowering 4 weeks before other

so late year i had to plants and one was done 3 weeks before the other. from the one that finished first i gor a couple seeds. and germed them for this year. and same thing 2 plants and one is 4 weeks ahead of the other. i just think that this is a bit weird. i know about genetics and all but same strain 2 years in a row? and how did i even get seeds anyways. there are no males within 20 miles

Plants can fertilize themselves, and seeds aren't always similar. In fact, they rarely if ever are identical.