It could be "nestbox eye", which is just a slight eye infection. For now, clean out the place where you're keeping them. If they're in a nest box, sometimes the momma starts using it as a litterbox, which can cause eye issues in the babies that are in there all the time.
You can also give an antibiotic eye ointment while you're waiting for the vet appt. At farm supply stores, you can get teramycin eye ointment, or you can get a triple antibiotic ointment at the human pharmacy store (neosporin). Make sure it's just plain old teramycin or neosporin in an ointment form, not a cream, and not containing pain meds as well. I would still take her to the vet to make sure that's what it is, but for now you can try that treatment.