I know you said the breeder had wormed them prior to you collecting them - do you know what they were wormed with? Was it an oral wormer or an injection?
What breed are they and what age are they ?
Are they eating, drinking and pooing normally ?
Are they bright and lively?
Do they have a temperature ? (it should be 38-39C)
It sounds like it could be a combination of things, but without photo's (and sometimes even with photos) it is impossible to say what it might be - come back with answers to the above questions and some of us might have more of an idea, but I suspect it's going to be a vet visit