There are many reasons a tree may decline. Park strips are tough environments to survive in. Water and available rooting space are likely limiting factors to their growth. A good place to start is in checking to see if the tree is receiving adequate water. Larger trees certainly need more water than small trees and all trees will require more water when temperatures are high.
The Utah State University Extension Service at the Ogden Botanical Gardens located at: Utah State University Extension Office 1750 Monroe Boulevard Utah, Ogden 84401
Utah State University Extension Services offers a plant diagnostic clinic every Wednesday from 3 to 6 p.m. May through September where residents can take samples for diagnosis and plant care advice. Extension employees are also available for horticulture related questions at 801-399-8080. They are on-site at the Gardens March through October.
The City Urban Forester is also a resource to be used and can be reached by calling Parks at 801-629-8284.