Certified GKH Gardening Expert
Yellow leaves usually indicates overwatering or underwatering. They need water two or three times a month. In the case of shamrocks, they may be going into a period of dormancy when the leaves will die back. During that time of rest it needs darkness and little water. It will resume growth when the dormancy periods ends. Depending on the cultivar, this could be a few weeks to a few months, most often in summer. When I had one, it died back off and on during the year then came back with new growth and flowers.