No, injectors should not clog or degrade in a year, but I don't know the quality of your fuel. All US gasolines have deposit control additives.

"Fuel driers" are primarily ethanol, which is a co-solvent that allows separated water to mix with the fuel and purge as the fuel is consumed. If you suspect your system fuel system has water, the engine could operate poorly until all the water is purged.

The best additives to clean injectors are those with Chevron Techron.

One way to test the injectors is to swap them with other cylinders that don't show rich operation and clean or install new plugs. If the dirty plug condition follows the injectors, then you likely have an injector issue.

Duke