Totally agree Gilly - in my experience I have found adequate hydration and warmth to be so important - I have a heated incubator that they all get popped in when dam is out for a wee etc and when these pups that I mentioned were so badly dehydrated, they were getting injected every 2 hours by me, in addition to what I could syringe in via their mouths and Stella was cooking with the heat I maintained both in the box and outside.
For bottle feeding, maybe I shouldnt endorse a company, but the best and most calorie dense replacement milk I found was that sold by Pedigree but I believe they no longer make it but instead it is made by the waltham/Royal Canin joint venture and sold as Royal Canin's milk. I firmly believe it was that that saved my totally hand reared litter as they only took off when I changed them onto it. I fed them every 2 hours for 2.5 weeks.They weighed only 3oz at birth - this was Firebirds litter. my usual working cocker birth weight is 15-17 oz (which I know is heavy)
Funny how 2nd litters go wrong, even though S coped with 2 litters, 2nd time round with only 5 she was so ill, with the section and then eclampsia and I had to help her feed these pups for a while inbetween pumping calcium in - think the pain maybe restricted her milk...Previous 2nd litters have also been hair raising at times. Dont know why..