Brewers are quick to believe infection is the cause of a particular off flavor and, while yes infections do cause off flavors, it is not the only reason.
If your water is minerally, particularly if it is well water, it can have a minerally aftertaste that at low levels can taste very similar to phenolic off flavors or even a sourness. The same could be true even if you're not using well water. If you're using tap water that isn't completely filtered you could have the same thing from some minerals in your municipal water supply. Chlorine-based chlorophenols can start out sort of sourish before they get really medicinal.
Before tossing your equipment I say brew a small batch on your equipment using your same process. Taste one at the usual time and let the rest sit for a few extra weeks. Taste again. If the flavor doesn't change, it's likely not an infection. If it gets overpoweringly medicinal, it's most likely chlorine in the water if you are using tap water. If it gets worse for any reason, it's definitely an infection.