Answer: It may be that your plants have outlived their normal lifespans and that's why they are dying. If you've changed your watering practices (amount, frequency, source) over the past 3-4 months, it may have affected your shrubs, or there may be an insect infestation (you'll need to carefully check for mites, etc.). Aside from these factors, I can think of no reason for mature cypresses to die off. I think you can safely replant healthy cypresses in their places. Just make sure the drainage is adequate (to avoid root rot). Best wishes with your landscape!
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