lol doesn't even look like there's a growth tip, if not it would take weeks of time for a new one to pop out. pictures don't show a good enough angle for that, but you'd be able to see one in real life.
I know some can't justify the cost, but planting 150% of the number of plants you need to fill a space is a good practice. that way a mutant or a weak plant doesn't impact the grow - as long as the 50% extra covers those issues, of course. Kill (cull) the weak! Plant issues are more common than people realize. 5% or more come out retarded in one way or another? it's a fairly high number. Some of those defects/mutations are of no concern.