Hi Marion,

Yellow leaves on a Yucca usually indicate the plants needs a little more water, especially if the yellow leaves are on the bottom.  Is the plant getting  new leaves at the top? Have you been feeding the plant during the spring & summer?

You might want to water from the bottom once or twice. Sit the plant in a deep saucer of water and see how much water it absorbs in about 15 minutes. Water may not be getting to the bottom of the pot when you usually water.

You can read all my care  tips for a yucca plant in the Popular   Houseplant section of the website.

https://www.houseplant411.com/houseplant/yucca-plant-how-to-grow-care-tips