Answer: Cape Jasmine, also known as Common Gardenia (Gardenia jasminoides) is picky about having soggy feet. It wants a well drained site so the roots do not get waterlogged. It also prefers an acidic soil.
If the yellowing is primarily on older leaves, I would consider either drought spells or soggy soil to be suspects. If the younger leaves are turning yellow it is an iron deficiency brought on by: a lack of iron in the soil, high soil pH, high soil phosphorus levels, or soggy soil conditions.
If soil pH is too high, consider using a chelated iron product or an acidifying liquid fertilizer such as Miracid. Correct water problems if they are deemed the likely cause. It may be worth the effort to lift the plants in late fall, bring in a soil mix with lots of organic matter to build a good raised planting bed and then reset the plant.
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