Failing hydrangea macrophylla bela bleu

    Does anyone have any idea what I’ve done wrong to my previously healthy hydrangea macrophylla bela bleu? I bought this a few weeks ago and planted it on 11th May in a deepish hole to which I added some peat free compost and a little horticultural grit. It’s planted under the dappled shade of an acer and a red robin on a north facing wall, but it does get a fair amount of sun. It doesn’t catch much rain because of the leafy canopy overhead, so I’ve been watering it daily. The soil is rich but free draining. In the same bed are some spring flowering bulbs, some french marigolds and some lettuce. It’s in close proximity to a camellia. When I planted it the flowers were fresh and healthy. Now they’re dying, and the leaves don’t look too fresh either. My husband thinks I’ve planted it too deeply, as the lowest flower is almost resting on the ground. He’s suggested I dig it back up and try to revive it in a container. Having already disturbed the roots once, I’d prefer to try to revive it in situ, though clearly if I’ve planted it in completely the wrong conditions and location I’ll have to dig it up and try again. Is it beyond retrieval? I’ve only fed it once (almost a week ago), with a general purpose plant food. Would more feeding help? Is the earth too compacted?