Why is my puppy sick?

i have two 6 week old chihuahua puppies. the girl has been sick for a few days off and on. then the boy became ill as well. they won't eat. they were eating soft dog food mixed with puppy formula. now they won't let a dropper come near them. they've been sleepy/mopey. vomiting and diarrhea. i hope to be able to take them to the vet at the end of the week i just need the money first. any help would be great.