It may be difficult to determine the problem over the internet and the images don't really tell us much. 

The reasons for leaf loss can be due to root issues, stem issues, or possibly insects. We don't generally see a lot of problems with atlas cedars, but occasionally they can have insect or disease problems. 

A root problem may be difficult to determine because it is below ground. Careful excavation around the roots and into the soil may reveal problems like poor drainage, root damage of some sort, or root rots. 

Careful inspection of the base of the tree, trunk and stems may also reveal issues. If the plant was planted improperly and packaging material was left on the trunk or around the root ball that could lead to girdling and restriction of water and nutrients to the rest of the tree. Trunk damage due to the freeze or fungal cankers could also reduce flow of moisture and nutrients. Look for splits and sunken areas along the trunk and stems. 

Spider mites are the only insect type pest I can think of that might cause similar symptoms. Inspect the leaves carefully for mites. They can usually be detected by holding a white paper underneath a branch, then tapping it to knock the mites onto the paper. After tapping, look for tiny specks, about the size of a pin point to start moving. You can also wipe your hand across the paper and if there are reddish streaks left on the paper you probably have mites. 

Eventually you may need someone to come take a look at it. You can contact the Oklahoma County OSU Extension Office to see if they have someone that can come inspect the tree or you can try a local arborist or other landscape professional to come look as well. The extension office may have some suggestions of professionals.

One other note. These trees are extremely close to the house. I don't know if these are a dwarf variety of atlas cedar or not, but generally these become large plants and even if it is a dwarf variety, they are way to close to the home. A common atlas cedar can reach 40 to 60 ft. tall, 30 to 40 ft. wide or larger, with age. The dwarf types are listed at reaching about 15 ft. high and 6-10 ft. wide over about 10 years, but can become larger with age. Just something to think about.