Neighbor across the street pruned hers several years ago and they never seemed to be happy again. Hers are bigger than mine, but they look brown too.
Holly Bushes Have Turned Kinda Brown – Are They Dead?
There are several pests and pathogens that can cause trouble on holly bushes. Examine the leaves and branches carefully to see if you can identify a problem. This article explains the most likely culprits: https://www.gardeningknowhow.com/ornamental/shrubs/holly/diseases-of-holly-bushes-pests-and-diseases-damaging-holly-bushes.htm