treating browning leaves on holly plant
Holly bush's leaves are turning brown and make the bush look dead.
Here is some information on holly problems: https://www.gardeningknowhow.com/ornamental/shrubs/holly/diseases-of-holly-bushes-pests-and-diseases-damaging-holly-bushes.htm
Take a look at your plants to see if you can identify any of these factors. If not, most likely your holly is suffering the effects of the tough winter. You're not alone; we're hearing more reports of holly leaves browning than any other type of plant.
You can remove dead branches now, but if the branches are still flexible, leave them to recover in their own time. This article on holly pruning tells you more: https://www.gardeningknowhow.com/ornamental/shrubs/holly/trimming-holly-bushes-how-to-prune-holly-bushes.htm