I did see both photos of your sad dogwood trees. I suspect the dogwood blight, dieback, anthracnose  of even crown canker disease is the cause. Dogwoods have been declining in health ever since the 1970's and they are very susceptible to fungal infections. The best treatment is to build up the health of your trees by watering at least one inch of water a week during the summer and keeping grass and other groundcovers about a food away from the trunk of your trees. Fertilize just once a year with a slow release plant food like Osmocote in late spring. Do not allow the soil to dry out as a stressed tree is more likely to suffer.  In most cases spraying with a fungicide has not been found to be effective in preventing the many dogwood wilts and diseases. Young trees like yours may be able to outgrow the problem with good care and proper location. As dogwoods are woodland trees they appreciate some shade in warm climates. If your dogwoods do not respond I would suggest you replace them with the hardier Korean dogwood or Cornus Kousa.  Keep growing, Marianne Binetti