Q.yucca plant leaves
Lower leaves on my yucca plant are turning yellow and brown. Is this a disease? What can I do for it?

Browning leaves can be just a part of normal aging of the plant or a more serious issue.
Here are some articles that will help you pinpoint the cause.
https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-turning-brown.htm
https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-plants-care-and-pruning-tips-for-pruning-a-yucca.htm