Well, I have one plant and to some extent one more that want to grow higher and faster than the others.
This is not because of bad light though as they recieve the same light as the others but it just seem to be in their genes to do so.

My stretchiest one is gonna be my top yeilder I am quite sure seen from the insane flower growth on it, dense and plenty of them. Even the side branches grow really big flowers on this one. Maybe my FIM'd one will beat it but I kinda doubt that, maybe.
I don't think you generally can say that stretch = lower yeild. I am quite sure that if it stretches because of bad or too distant light that will be the case though.

Puffzter