Luv, they need antibiotics. They should also be tested for calicivirus, not to mention a few of the other choice illnesses. At six weeks old there's a good chance there's an underlying cause if the whole litter is ill.
I know it's been a few days since you posted this, so I hope you got them to a vet. Eye infections develop quickly in cats and can lead to permanent blindness in even a few days.
they have a upper respiratory infection, not uncommon for little ones because their immune system is so low. take them to the vet right away! this can become pneumonia and they can die quickly if it turns into that.
they may need to be seen by a vet so they don't keep making eachother
and the mom sick over and over. do not give them people meds. most
are poisonous to animals!! good luck!!