Can you tell if a capacitor has leaked by dissecting it?

My JVC stereo is humming loudly. There are signs of an obvious
capacitor leak around three large capacitors on the board. Brown crust.

I replaced two large 6800uf 40v caps, but the humming remains. So I
pulled the third cap, a smaller 3300uf 35v unit.

For fun, I dissected all three.

Each large 6800uf cap had dark brown paper all the way through. Viewed
from the top, the spiral of paper was consistent in color.

But the smaller 3300uf unit, when the paper spiral was viewed from
above, the center of the spiral was a lighter color than the rest of
the paper.

Does this mean I have found the leaky unit?

I have no way to test them.