The other images from your shoot for this couple are nice and flattering.
I don't think the smoke in this situation, for an engagement, is very flattering in this particular composition. The smoke needs a context so it's not just some random flashy thing in the composition. In a lot of smoke photography, I see it usually used to add to an element of some kind, be it to exaggerate a motion, or mask an environment and add a mood, and it's often colored to do something there. The ones where it looks like someone found some leaves on fire doesn't really add to the composition for me.