My son is 12 days old and he has a red eye and yellow gunk is comming out of his eye. is it ok to give him tobrex (tobramycin)?

It may be: Always talk to your pediatrician first before giving newborn any type of antibiotics, even topical ones for the eyes. While this is most likely a blocked tear duct, if there is a concurrent infection they may want to culture it first and/or use a drop that does not contain a steroid as Tobrex (tobramycin) does. Start with warm compresses and tear duct massage first and then talk to ped tomorrow.