If your soil is very heavy in clay and you are watering too much, you could be drowning the trees and they are reacting the only way they can to tell you they aren't happy. If you dig your hole twice the size of the root ball, added compost material to enrich the soil and followed grower's instructions this could be a problem.Did you open up the root ball and loosen up the roots so that they would be able to grow out from the tree? Sometimes this is not done and could be part of the problem. Another is that 7 foot trees are difficult to transplant withour complications. You need to water them hard about every 3-4 days, but not everyday. If they were kept in a sun shelter before you got them, they could be suffering from sunburn as they are not used to the direct sun. There are so many possibilities that without further information it is hard.