You can see the impact the shade and/or the water demands of the tree are having! I wonder if switching them around would allow the smaller two to catch up.
"What is hateful to you, do not do to your neighbour".
I wouldn’t dig them up and move them, that will only check them even more. I’m sure they’ll catch up, they’ve got a lot of underground growing to to do before they make top growth.
Depending on where you live, very lightly prune early spring next year, that’s if they’re big enough, if not leave them until the following year. They’ll still be getting established.
Gardening on the wild, windy west side of Dartmoor.
When I bought my "Annabelle" from Bressingham Gardens many years ago the catalogue stated that it would be "best in full sun with good feeding" and I have found that to be largely true, unless the site is too dry. I have several plants grown from cuttings now in different positions and find that the best way to prune them is to take down some stems right to the base in the Spring (it is Hydrangea arborescens so flowers on new wood) but just trim others to the required height of the bush. This way you get the larger flowers on the new wood but the few older stems you don't prune support the floppier ones with the bigger flowerheads. Your plants are still very young and I would just keep them well mulched until they are a bit bigger, water them well in the Spring and perhaps wait to prune until they are in their second or even third season after planting, just removing any dead or diseased wood in the meantime. It is possible that the reason some plants are doing better than the others is that they are getting more light, moisture or food, so if you focus your attention on the others they should catch up a bit. Hydrangeas have roots which are close to the surface so benefit from mulching more than most...I use home-made compost and a bit of manure so that they are also fed as well as kept moist.
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When you don't even know who's in the team
S.Yorkshire/Derbyshire border
I’m sure they’ll catch up, they’ve got a lot of underground growing to to do before they make top growth.