Those are great temps and humidity. You can google temperature diff to learn about how the differnces between day and night temperature affects your plants. Long story short..a larger diff equals greater stretch.
Plants are like cold blooded animals in a way, the chemical reactions and processes are endothermic and therefore their rate increases with temperature until some limiting factor is reached. That is why people use co2, it allows higher growth rates at higher temperatures, without co2 and temp of 80+ there is not enough to complete reactions.
I prefer a slightly higher humidity in veg, like 60-70. It is slightly "easier" on the plants and they seem to stretch less. The more compact you can make a plant the higher it's capacity for producing carbs is for a given amount of space.
Plants don't "decide" to do things, they simple react to their environment. When it's drier, the evapotranspiration rate is higher and they are absorbing more water. Which is fine unless your nutes are too strong. I have seen tips burn after turning the Dehu on.
If you want the sweetest smelling and most potent buds that your genetics can muster, I would follow the advice above...low humidity in the last couple weeks and do NOT let temps get above 78. Also, letting your plants experience some moisture stress can increase resin production to so small degree. The degree depending on the genetics.
Their have been a couple of legit studies that show that MJ plants likely produce resin to (attract pollinators) but also to fend off the desicating effects of dry wind and low humidity for those strains that originated from places like Pakistan.
Cheers
