Link is fast bud toxicity and deficiencies. also has other sites about the same topic.
" Growing cannabis is a lot of fun until your plants start dying without any rhyme or reason. Well, there certainly is a reason, but you don’t see it at that point of time. And, this can be very frustrating, especially if you’ve cared for the plants like they are your own children. Among the many problems ailing plants, cannabis nutrient deficiencies are the most common and can end up causing nutrient lockout.
A nutrient deficiency refers to any problem caused by the lack of macro or micronutrients caused by an improper pH or simply by underfeeding so It is important to supply your Cannabis plants with the perfect balance of primary and secondary nutrients, as well as trace elements. As plants mature and enter different stages of their lifecycle, knowing what to feed your plants, when to feed them and why they need that nutrient in the first place can be a huge difference-maker in the overall quality of your crop, including the health and vigor of your autoflowering cultivars.
In this article, we explain the different types of nutrients, signs of deficiencies, and what to consider next time you are feeding your garden." Source