Good point on the possibility of a broken line between the well and
the house.

You might check the likely line "run" area between the well and the
house see if you find a soggy patch of ground, indicating a leaky
pipe.

Another method is to pump compressed air through the line and see if
you can hear the hissing as it escapes at the break.

Finally, if it is not too big a run, you can dig carefully along the
line of the pipe and see if you find anything. In my case the well is
about 130 yards from the house, running through heavy trees -- so none
of the above really works at my place.

If I had to bet, I would guess you are just suffering from an usually
dry summer. You can always check the static water level in the well
and see what is going on from that end, also.