We think something is eating the top or bottom of the leaf, then it is drying out and splitting.  Looks like it has been going on for awhile.  Could also have some hail damage from the recent hail we have had.   The insect damage could be from beetles, earwigs, or leaf hopper.  I would get up close and personal with your plant and see if you can find an insect.  Then bring in the sample or send a picture.  We cannot give recommendations on control without first figuring out what insect type it is, plus since the plant is blooming, we do not want to hurt the pollinators.  Good news is this is a tough shrub.