Can a new manufacturer of the same meds i've been on cause hives or an allergic reaction? only new med i took was mucinexx dm. maybe mucinexx is prob?

Possibly: If you started a new medication, then it is possible for the new med to cause allergic reaction. Stop using the new medication and see if the hives go away. There are some people who have allergic reaction to generic forms of some medication as well. So of you were switched recently to a generic version, go back to the brand name. I would try the first option of stopping Mucinex (guaifenesin) and observing.