F1 hybrid autoflower seeds, made by crossing two stable inbred parents, tend to show a burst of vigor that later generations lose, and it is visible by week two. The catch is that a true F1 needs the breeder to maintain both parent lines, which is expensive, so the term gets slapped on packs that are really F3 or worse. How to tell a real F1 from marketing, and which breeders keep proper parent stock, is discussed on https://turboautoflowerseeds.com. Uniformity in the tent is the practical payoff.