Is this a newly planted tree, or one that has been established for some time? Dogwood is an understory tree, meaning that is grows best in at least part shade. In full sun, it will be under stress. The browning and crinkling of leaves may simply be drought stress. Even if watered well, the leaves may scorch in full sun. Yellowed leaves with green veins may be an indication of iron chlorosis. The chlorosis may be due to high soil pH or other stress factors. If the pH is too high, you may be able to lower it by applying sulfur to the soil. There are also iron chelates that may be applied directly to the foliage to green it up. However, unless you correct the underlying stress factor, the chlorosis will return.