It might be worthwhile to have a certified arborist or licensed tree expert with experience diagnosing conifers assess the trees, since they can examine foliage and trunks for insect pests (borers or scale insects) and the trunk base for girdling roots or other physiological problems. Unless the root zone got too wet for a prolonged period (not very likely this year, given the drought), fungal root rot is not likely, nor is a fungal infection of the trunk or branches. That said, there is a fungal canker disease called Botryosphaeria that can infect plants that are under stress, and such stress can include drought, so we can't rule that out. (The linked page focuses on Rhododendron and other shrubs, but this fungus can affect a much wider range of species.) If that were present, there is no fungicide cure, nor would there be for other fungal infections, or, similarly, no insecticide cure for wood borers, though scale could be treated. Dieback would need to be pruned off regardless of cause, since entirely-brown branches will not recover. Brown branch bases that have green, live tips will still be capable of growing (at the tip).

It is normal for Cryptomeria to shed some old branches/branchlets as they age, and it's also normal for old foliage on all evergreens to shed yearly, turning brown (or yellow first for pines, spruces, hollies, and such) and falling off at some point, usually autumn or spring. We've seen healthy Cryptomeria shed some surprisingly long branch sections in their lower or innermost limbs as part of their normal aging process, but without images to examine how extensive the browning is in your case, it's hard to say if it is concerning or not. As a tall-growing evergreen, they do naturally and gradually develop a bare trunk for some height, just like (though not as drastic as) mature white pine trees do. Examples of high-limbed Cryptomeria can be seen in plantings at the U.S. National Arboretum, for example.

Occasional watering should have helped to alleviate some drought stress, though with this drought being present essentially all of the growing season for most areas in the state, it might not have been enough to alleviate all moisture stress, or soon enough to prevent some foliage loss, and higher-than-usual amounts of autumn leaf shed may be a result of prior drought stress. Our Watering Trees and Shrubs page provides guidance for determining when to irrigate, if useful.

Miri