Ask Mr. Smarty Plants

This seems to be the season for problems with ash trees; this is the second question on this that we have answered today, so we trust you will forgive us if we plagiarize some of the previous answer. According to this USDA Plant Profile on Fraxinus velutina (velvet ash), while it is native to Texas, it is not native to the Houston area, or even close, as seen in this USDA Plant Profile of the tree. Since you have  had the tree for 14 years, that is unlikely to be the cause of the decline, but we will try to give you some resources to figure it out. 

Ezine articles Arizona Ash Trees - "Arizona ash trees, like many other plants, are susceptible to various pests and diseases. These include cankering, mildews and various fungal infections, leaf scorch, rust diseases, and pests such as mites, webworms, carpenter worms, and borers. Ash trees are particularly vulnerable to Verticillium wilt, which is a soil-borne fungus. In some parts of the country (primarily the midwest), the emerald ash borer has killed many tens of thousands of ash trees. Luckily, Arizona ash tree varieties have not yet been affected by the destructive emerald ash borer. Trees that endure poor environmental conditions are more vulnerable to these problems, so it is important to keep the tree's defenses up by watering and fertilizing adequately.

Purdue University Verticillium Wilt of Shade Trees

USDA Animal and Plant Health Inspection Service Emerald Ash Borer

University of Illinois Extension Ash Tree Problems

Because Houston, in Harris County, is not a natural habitat of  Fraxinus velutina (velvet ash), our best guess would be the problem is related to the moisture in the soil, to which the tree is not accustomed. This could lead to the Verticillium Wilt or to other fungi attacking the tree. The tree is fast-growing and short-lived, but it usually lives longer than 14 years. If it is indeed reaching the end of its lifespan, that could explain the dropping of leaves and seed pods. Since we are not plant pathologists and cannot see the tree, we would suggest you contact the Texas A&M AgriLife Extension Office for Harris County for more ideas on the treatment of the tree.

Images of Arizona Ash from Google