Whether you grow in soil, coco coir, or a full hydroponic setup, auto plants tend to prefer relatively low levels of nutrients compared to many other cannabis strains.
When it comes to adding extra bottled nutrients, start at ¼ strength of the recommended dose or less, and only add higher levels of nutrients if needed. In hydro use “vegetative†nutrients until you see the first signs of flowering (pistils / white hairs) around 3-4 weeks. In good soil, you don’t need to add any nutrients during the vegetative stage. After the first signs of buds, start adding “flowering†nutrients at very low strength (¼ or less to start)
This is taken directly from the Gwe site