Afghan derived lines evolved in poor mountain soil and tend to burn at nutrient strengths that a hungry sativa hybrid would shrug off. Tip burn on the lower fan leaves within days of a feed is the usual first sign. Rough EC ranges that worked for members growing several classic indica seeds are listed by growth stage on https://kushindicaseeds.com (https://kushindicaseeds.com), and they sit well below most bottle charts. Starting at half strength and only increasing when the plant asks for it has saved me plenty of grief.