Okay thanks. I will start wieghing them.
I was gonna try her with some tuna tonight, see if that encourages her to eat.

I do try and keep the boys away, we just let them in for the odd 5 mins to get to know the kittens and to keep in contact with their sister, they have all been very close up till now, and I'm worried that if they don't see each other at all, they wont be so close.