Baby rabbits full of sores

I have 6 baby rabbits (2wks old) they have some kind of skin complaint. looks like warts but full of yellow pus. one is particularly bad with them all over. i have been to the vets today they do not know what it is - they have swabbed them and it is not parasites. Any ideas? Also they want to give them anti biotics, is that harmful to babies that age
   
thanks