That far apart it probably won't work out very well to foster the whole litter but maybe fostering a couple will help take some pressure off the mom that isn't doing so well. I think it's a good idea to boost her protein while nursing even if she wasn't struggling, so the 32% dog food will probably help. I'd just watch what kind of dog food, some is really healthy for rats and others is really unhealthy. Corn isn't good for them (or dogs for that matter), which is present in most of the cheap dog foods and even some of the pricy ones.