You can't divide them - they are small bushes, not herbaceous perennials. They'll need to rest and make the buds that will be flowers and leaves for next year. You can dig them up if you need the space where they are, but you'd need to keep plenty of roots on them and pot them up in ericaceous compost and in big enough pots, and they'd need more care (careful watering and feeding) if you do that. They'd be best off if you leave them where they are, feed with a suitable feed for ericaceous plants, water them when the weather's dry and enjoy their flowers next year as well.