Thanks for everyone that replied to my post.
I have changed Maisy onto a different food, recommended by my local pet store.
Also stopped giving her the puppy milk. Both mum and pups are feeding well, although she is quite happy to leave the pups when ever she gets the chance.
I know it's still early days, but so far so good, all the pupsters are putting on weight, some are just gaining it faster than the others.
The one I was worried wasn't feeding enough is actually gaining more than the others.
I expect I will ask a few more questions and I appreciate all the advice I have already received.
