Sandy,
It's wonderful to hear the pups are doing good still. It still amazes me that the vet didn't recognize your girl was pregnant.

Anyway, before starting to wean them to solid food, I would wait to get the diarreha cleared up. Then start weaning very slowly. Make a gruel that is mostly milk (whatever you are using currently). Take the puppy food and blend it into a very fine powder consistency in a food blender. Whatever they are getting now, make it 3/4 milk and 1/4 food. Make sure the food is expanded with the milk. Make it a little warm but be careful not to get it too hot. Too hot can kill necessary enzymes.

After they do fine with this for 3 or 4 days, change the ratio to 1/2 and 1/2. Then again after 3 or 4 days, change to 1/3 and 3/4. Go slowly with each change. Make sure you are weighing the pups and each is gaining before advancing.

Finally you are going to eliminate the milk all together. Usually the pups should be around 5 weeks by then. Grind the food still but not as fine. Swell the food with warm water. You want to avoid bloat. Little by little over the next few days swell the food without grinding it. Then eventually by around 6 weeks or so try dry kibble. Make sure you start giving them fresh water around 4 1/2 or 5 weeks along with the food. They should be drinking before you start giving dry kibble.

Let me know if you have any questions and keep up the good work.