This looks normal in pattern but excessive in quantity, though nothing will reverse the senescence (shedding of old leaves) once it begins. If the trees were not watered regularly during this summer's significant drought (which has still not abated), then that could be a contributing factor to why so many of the older leaves are shedding. Making sure the plants get enough soil moisture going forward will help to at least preserve the buds lying dormant on the stems for next year's growth. (Our Watering Trees and Shrubs page provides guidance.) It will also reduce stress on the roots, because if root health declines, foliage will be affected.

All evergreens shed their oldest leaves each year, either in spring or fall, but usually their healthy growth is dense enough that not many of those browning leaves are visible from outside the canopy. As to why these particular Falsecypress are so sparse, current shedding aside, it's hard to tell, but lack of enough direct sunlight in summer, root loss from over- or under-watering (or damage from digging in the root zone in the past few years, if applicable), or some other long-term health issue might be a factor.

For now, other than checking the root zone for watering needs, nothing can be done, and eventually the browned needles will fall off on their own.

Miri