Sounds like your tree(s) is being damaged by your being steered into trying to follow a rote schedule that does not allow for variables in weather, site conditions and what state the plants are in on arrival. They may have been getting too dry before you even got them, and needed to be given several good soakings to try and re-wet the original field- or potting soil rootballs. Poke around in the dirt right around them to see if it is moist all the way through or in fact partly dry. Once determined to be moist or made moist all the way through, water as often and heavily as is needed to maintain this condition. Keep periodically digging into the soil if you have to in order to keep on top of things.

Here is a link that might be useful: Planting fact sheet.pdf (application/pdf Object)