'04 with 1 dim headlight

After recently replacing what I assumed was a blown bulb, the new bulb lit but was very noticebly dim compared to the opposite. I had purchased 2 new bulbs intending to replace both so tried the other thinking it was bulb that was somehow bad. Same result. Visual inspection of wiring to the headlight assembly, figuring perhaps the wiring had rubbed thru against the battery over time but no obvious signs of a problem. As a last attempt installed the first tried bulb in the opposite headlight socket and it lit quite normal.
Prior to this have never experienced any problems. The vehicle was however in for tires that day and the vendor did their routine inspection of the assorted norms. They did say the battery was running a bit low but that doesnt seem likely to affect 1 headlight.
Recommended course of action?
While I do have some automotive repair experience it is primarily with much older vehicles.
Any suggestions/ info will be much appreciated
don B