I am having some difficulty with my loropetalum and crepe myrtle. the leaves are drying up and falling off I've got to beleive its from a frost we had in mid April. the only other thing that I can think of is that I may have had a little drift from Weed out with trimec, but would that cause that much damage to these plants? Anybody have any ideas about what i can do about it?

by the way the frost hit when the plants where still potted.