cheap timers, fucked breaker, crap soil, and getting too high while tending to them. got powdery mildew, spider mites, sprayed them but didn't rinse later before lights on.....leafs didn't like that for sure. Didn't have any type of feeding schedule
Good luck with the grow! I am on my second grow and will be cloning and starting new strains till I find what I like......and hope to learn more "what NOT to do's" along the way