Coco coir sits between soil and hydroponics, and not every strain feels at home in it. The medium needs frequent feeding and holds little in reserve, so vigorous, fast drinking plants tend to thrive while slow growers can stall. When choosing strains for coco, I look at the growth vigour notes at https://budweedseeds.com (https://budweedseeds.com) and lean toward hybrids described as strong feeders. Calcium and magnesium deficiencies are common in coco regardless of genetics, so supplements are almost unavoidable.