Dear you have not mentioned ...

Dear you have not mentioned what type rock type you had tapped? Its seems like fracture aquifer i have seen similar cases within fractured aquifer. Also may i know type of drilling fluid used during drilling? Any way during pumping of of the productive well start monitoring the second and see are you getting any DD there or not. If its a fracture aquifer then the nonproductive well might missed the productive fracture system in that case getting sustainable yield wont be a possibility, you can try another DD test with a lesser flow and see if you are getting any stability in the DD, and form there you can drive a safe yield with lesser flow. If its because of drilling fluid use of bentonite as media then you might clogged the productive zones, in that case there are some chemical treatment is available and those are little difficult option considering drinking water well and another option is effective well development. Good luck