I don't know. There seems to be a lack of new growth while the old leaves die of old age. What have you been feeding them?

Are they all in pots? I would remove one from a pot and examine the roots.

Could you
give us your general location? It appears that the most recent new leaf growth
was stitched together and prevented normal growth. If that is the result than
you may have a late stage canna leaf roller infestation. Location please!
Kent

"greater and lesser canna leaf roller ... be Japanese beetle "

Just for my edification, how is it that these pests elude observation so easily? From what I read, they are large enough to be seen. And, a non-casual observer would unroll a leaf to examine the inside.

Aruzinsky,

How is it that these pests elude
observation so easily? From what I read, they are large enough to be seen.

Most plant or animal problems, be it disease, pest or virus, typically start
out very small and IMO are not easily observed in the beginning. (Conception or
pregnancy is not obvious initially but progresses to the obvious over time).

How many larger leaf roller eggs
the size of a pinhead on the underside of a canna leaf would it take for the
most non-casual observer to see the beginning of a problem? The hatched out
larva are nearly colorless and less than 1mm long and typically feed on the
underside of the leaf.

The night flying moth of the lesser leaf roller typically seeks to find
a young emerging canna leaf still in the whorl stage; craws inside to deposit
its many eggs then emerges to tightly stitch the whorl closed to prevent unfurling
and expose its eggs and hatched larva.

Both the dedicated as well as the casual gardener often finds only
limited time to devote to the care and observation of plants. This often leads
to recognizable problems being delayed.

Please keep in mind that we are only addressing what appears to me to be
the major problem/not necessarily the only issue posted above.

Kent