Thanks to you all for the advice. I suppose I just have to keep my fingers crossed for them. I have put them in the bathroom and filled up the bath with hot water and placed just the one kitten in a laundry basket with blanket and he is breathing much better now but he is very quiet so I don't think it looks good for him. He seems weaker than the rest. The others are with mum just now as they seem bright and strong and can breath. They have sticky eyes. I am sure it is calicivirus as it has happened before a while ago but I thought it had gone. I had no idea it would affect such young kittens. I bought in a female cat which developed a touch of cat 'flu after a few weeks and she didn't get it from any of my existing cats as they had never had it before, It was too late to stop it going to the others and they developed a touch of it too. I was angry but can't do anything except re-home them which is drastic.

Will keep you updated.