Front ballast tank (not bow) requires the fuel tank to be removed to access it.

A tank crack is rare but possible. Again, i believe you but it is vert hard to see through the access holes. I would check lines and fittings first. Buy a bore scope camera from Amazon for $20-30 and use it to find the leak first. Still might need to pull things out of the way to fix a fitting but at least you will know exactly what to fix.