Q.Newly planted crepe myrtle bark slits or gashes
A month ago I planted 7 crepe myrtles in our backyard. I have noticed 2 of them have developed near the base ‘slits’ or ‘gashes’ in the bark. One of them has 3 small slits or gashes, and the other has at least one. They each are less than 2 inches in length. At first I thought maybe an animal was slashing at the tree, but they look naturally formed to me (i. e.they are relatively clean, not surrounded by scratches or other marks). Is this a problem I should be addressing (such as overwatering or a sign of disease), or is this part of the natural exfoliating process of the bark (or otherwise harmless)?

Certified GKH Gardening Expert
It is very possible that these are "stretch marks" on the trees. If they are happy, they may simply be growing faster than the bark can keep up with them. As long as these gashes are not girdling the trees, they should not pose any issues. As a preventative measure, I would treat the gashes with a fungicide on a monthly basis until they heal, as any wound on a tree can be an invitation to disease. A fungicide would help prevent that.
I would also not write off animals as the cause. Deer and rabbits have been known to take clean strips of bark off trees, especially young ones. You may want to put some guards around the trunks of the trees, just until they get a little older and established.