Q.My Holly Bush/tree Has A Lot Of Yellow Leafs On It. Most Of Them Are Falling Off But Some Stay On The Bush. What Am I Doing Wrong?
Lots of yellow leaves on my holly bush/tree. Most of the yellow leaves are falling off but some remain.

Certified GKH Gardening Expert
This, really, depends on where and how this looks like it is happening. If this is, mostly, interior leaves and not leaves on the ends of the branches, then this can be normal leaf loss, in spring. These articles will offer some more information on what is considered "normal".
https://www.gardeningknowhow.com/ornamental/shrubs/holly/holly-leaf-loss-in-spring.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/holly-yellow-leaves.htm