Try to grow up in an attic. Couldn't fit any tent amongst the scissor trusses, had to construct the enclosure, (lots of work). Always bumping my head, shins, knees on something. Humping the water, neuts up the fold up ladder. Going up/down the ladder untold amount of times during grow. Not paying attention the the RH during bloom. Trying to grow too many plants at once.
Not topping soon enough. Not using enough lights for bloom.
(Abandoned the attic, reclaimed some space for a grow on the first floor, got some 4x4 tents, grew more, easier and with fewer plants, much better results all around).