The answer to 'why is my garden yellowing' is that it is likely due to a nutrient deficiency, overwatering, or disease. Yellowing leaves can be a sign of nitrogen, iron, or other nutrient deficiencies in the soil. It can also be caused by too much water, which can lead to root rot and prevent the plant from absorbing nutrients. Diseases like fungal infections can also cause yellowing and discoloration of leaves.
If the yellowing is localized to just a few leaves, it may be a natural part of the plant's life cycle and not a cause for concern. However, if the yellowing is widespread or the leaves are wilting, it's a sign that something is wrong and needs to be addressed. In these cases, you may need to adjust your watering, fertilize the soil, or treat for pests or disease.