Hey brother most of time this is straight up genetics that is defenitely some sweet looking leaves . The other would be that anything under 60 degrees can bring out the purple in certain strains not all of them ..your girls look very healthy so I would say that it is the genetics ,did the buds you got seed from have purple or can u find out if the grower I know that ain't easy can tell you if the purple is normal from the strain might be a long shot..cheer from Canada ..