To keep your calibrachoa leaves from going yellow, fertilize your calibrachoa pots with a half-strength all-purpose fertilizer to get them growing again. For calibrachoa in pots, it is recommended to use an all-purpose fertilizer such as Miracle-Gro because it consists of all the necessary nutrients that calibrachoa needs. Avoid applying the fertilizer directly onto the leaves or flowers, as it may cause burning or damage. Use a liquid fertilizer once every 2-4 weeks to keep your calibrachoa in the best shape, help it bloom, and keep its leaves from going yellow. Watering the calibrachoa thoroughly after applying the fertilizer is essential to help the nutrients reach the root system effectively. Proper watering and regular fertilization will contribute to healthy growth and vibrant blooms in your calibrachoa plants.