Improper Watering
One reason why an Easter lily might begin to turn yellow could be due to too much or too little water. If the Easter lily’s soil feels soggy and drenched, then you might have overwatered it. Overwatering causes root rot, leading to the yellowing and dying of lower leaves. If the soil feels crumbly and dusty, the Easter lily received too little water.
Feel the soil before watering the Easter lily to avoid these water issues. Water when 50% of the soil volume is dry. Water thoroughly and discard excess water to avoid root rot.
Dormancy
Part of the Easter lily’s natural life cycle includes dormancy. This period of dormancy happens once a year—typically in the winter, but it can also occur in summer. It is normal for the leaves of an Easter lily to turn yellow before shriveling and falling off as a response to dormancy. If your Easter lily is going dormant, reduce waterings to about every 5-6 weeks. After this rest period, resume regular watering to promote growth heading into the spring.