I was under the impression that it was the magical
properties of the Water Of Life that made her cooking
edible, and that wouldd account for her return to bad
cooking once the spring dried up.

Again, in the manga, Akane cooks a mean that Ranma calls normal *before* she
leaves for Ryugenzawa.  She cooks the meal at the Tendo home without the
Water of Life, and no one wants to eat it assuming it will be bad, but it
turns out to be "normal".

Part of what motivates Ranma to go after Akane when she runs away to
Ryugenzawa is his guilt over his refusal to even try her cooking.

-Mat

-Richard