Bio fouling can completely plug a pump, or the fractures, or both. You need to have the pump pulled, and then determine which is the problem, the pump, the well, or both. That's the first step. I've had good luck with a product called Boresaver plus. Its an iron bacteria treatment, that we brush and swab a well with, then airlift out...best left to professionals; but its probably cheaper than a new well. It's also very possible it's just the pump.