Q.Blue Prince Holly
I have 3 Blue Prince Hollies and two of them are losing their leaves, which are green. Please help; they were installed last year and I don’t know what to do for them. I live on Long Island and they have a sun exposure.

Most issues with pests, disease or environmental will present with some more issues with the leaves. Are the leaves yellowing, have spots, color changes?
It is recommended to clean up and dispose of any leaves that have dropped to prevent the spread of disease.
Here are some articles that discuss the most common issues with Holly.
https://www.gardeningknowhow.com/ornamental/shrubs/holly/diseases-of-holly-bushes-pests-and-diseases-damaging-holly-bushes.htm
https://www.rhs.org.uk/advice/profile?pid=175