Poor babies. I would be tempted change vets, someone who has lots of
experience with rescue kittens. Clavimox is harsh stuff for small
kittens; your idea to reintroduce lactobacillus is good (you can get the
stuff at any health food store). Some other things you could try from
your vet are albon, which sometimes helps heal the gut (and will knock out
coccidia while it is at it -- coccidia can be hard to detect and often
flares up after worming). Also low-residue food (wet and dry, if the
kittens are old enough for kibbles). Also ask your vet about rehydrating
the kittens as needed. Diarrhea brings on dehydration very quickly, and
dehydration kills quickly.

Good luck. Let us know how it goes.

Sharon Talbert
Friends of Campus Cats
Seattle