seeing their Cannas looking poorly... I shall relax and let nature take
its course

Might as well, I've had cannas growing for years beside my water tank where
they get plenty of water year round, and a big drink each week when I pump
from the well up to the house and overflow the tank. I've pulled them out of
the ground at all sorts of places and planted them at home with a range of
different colours etc. The red ones seem to do better than the rest here in
the clay soil and Toowoomba type weather that ranges from hot summers to
cold frosty winters. In winter they do die back, and a trim with the
lawnmower does them proud when they start to shoot back in spring. Even if I
forget to hit them with the mower, the cows eat them just after they flower.

They like plenty of water and sunshine. Some of the best examples are
planted near leaky taps.

Hope this helps,
Peter