Holes in my Hydrangea

I have two hydrangea in a shrub bed in the front garden growing side by side with each other now in their second year. Both seem to be growing painstakingly slow (was under the impression they were very hardy and quick to grow) one is doing well in so far that it is healthy looking but the other shrub has holes in a lot of its leaves and isn’t as full with leaves as the other, just wondering if you can tell me why there are so many holes on the leaves and what I can do to remedy this. They are hydrangea macrophylla mophead variety. Look forward to hearing from you.