They look as though they need replanting, re pot and add plenty of organic matter / leaf mould, yes keep moist but dont over do it, have you moved them into a full sun situation ? do better in a semi shade situation, leaves look a little chlorotic so you could give it a feed of sequestered iron.

I'd be tempted to knock them out of the pot and look for Vineweevil grubs. they certainly look as if they need a feed. give them a dose of Epsom salts [Magnesium sulphate] this will help green them up too. They should be happy in semi shade. So perhaps they need to be moved back to where they were.

Hydrangeas don't like being cut back hard. Maybe this is why they are looking sad. Only cut them back by about a third to the strongest bud in late Feb or early march. But they really do better in the ground.