Leaking water tanks

The tanks on my 1972 hull number 2 leak, albeit fairly slowly. They lose about a gallon a day, which has been sort of tolerable to date. The ends and top of the tanks are OK. The water comes from the midline of the boat, under the aft tank bulkhead. I'm guessing that a seam is opening up along the centerline. Has anyone done a successful seam repair on these tanks?

Thanks