Orchid leaves turning yellow can be caused by several common factors including natural aging, overwatering, underwatering, exposure to too much direct sunlight, temperature stress, nutrient deficiencies, repotting shock, and infections. Here's a brief overview of the main causes and remedies:

• Natural Aging: Older leaves naturally turn yellow and fall off as part of the orchid's life cycle.
• Overwatering: Excess water causes root rot, preventing nutrient absorption and causing yellow leaves.
• Underwatering: Dehydration can also lead to yellow, wrinkled leaves.
• Light Exposure: Too much direct sunlight can scorch leaves, leading to yellowing; orchids prefer bright, indirect light.
• Temperature Stress: Extreme hot or cold temperatures and fluctuations cause stress and leaf yellowing.
• Nutrient Deficiency: Lack of nitrogen, magnesium, or iron can result in yellow leaves.
• Repotting Shock: Post-repotting stress can cause root damage and yellow leaves.
• Infections: Fungal or bacterial diseases cause yellow spots and leaf deterioration.

To fix yellow leaves, adjust watering to about once every 7-10 days in winter and twice a week in summer, ensuring excess water drains well. Keep orchids in bright but indirect light with temperatures between 50°F-85°F and humidity around 50%-70%. Fertilize with balanced fertilizer 1-2 times a month during growing seasons. Remove fully yellowed and dead leaves gently to maintain plant health.