Shouldn't really be shedding lots of leaves, but more info is needed - are they in pots or in the ground? In an exposed, windy situation? Are they 'Little Red Robin', the dwarf version, or Red Robin? Any chance of a photo?

Thanks Bamboo will try to get a photo uploaded as they
are getting worse by the day.

I have added some photos which were taken today Monday 18th March.

Looks to me as if new growth arrived and then the weather got really cold again, and the plant has responded badly. Wait till winter is over (whenever that will be, I'm beginning to think it'll never be over) and the weather warms up, say mid to end of April or early May, then give it a good cut back and a feed. It should respond well and put out new growth.