This is fairly typical variation due entirely to the individual seeds genetics and not a problem or unusual occurrence.
Even seeds from the same strain, taken from the same packet, will show different flowering styles and also can have slightly different nutrition and water needs.
You don't have anything to worry about, this is generally known a "phenotypic variation".
Nice plants by the way, you sure can't beat sunshine, soil and the great outdoors!
Cheers, Organoman.