Over the last 2 months I have noticed some significant holes in my 3 year old plant. I fed it with liquid fertiliser for Azalea, Camellia and Rhododendron about 4 weeks ago to see if this would help. What could this be ? I don't think it's slugs or weevil because of the way the leaves look burnt.

The plant is a half-shady spot next a fence so isn't exposed to the elements.

Any ideas ? Pictures attached.