Its normal for a plant to drop any number of leaves during flower, some plants even drop em all damn near
, as the plant loses all its nitrogen and diverts the energy to the buds the leaves will yellow and die, This is why its not good to add much nitrogen during flower, typically 1 - 2 - 3 ratio. Too much nitrogen in the plant will make the smoke harsh.
Just my two cents
Look foward to some tasty smoke in my opinion
Wonky