You can put your hand on the highest buds and if you wouldn’t want to leave it there for a good while, the plants probably won’t like it either. You want the leaves to be pointing slightly upwards with a nice V shape in the leaves with no minimal ruffled edges. That lets you know the plants are taking all that they can. If you see drooping starting later in the light cycle(day) then the light is to close or hot. Happy Growing!