I would think you could either leave it until next year, or dig it up now and see what's happening. It may be you have a twisted clump left and the remaining rhizomes just aren't as strong and healthy as the ones you removed.
Cannas are hardy.........if you dig it up, just try to keep as many roots as possible and water well afterward.

Your cannas may still be too crowded. Or perhaps they need to be fed. They are heavy feeders. And they love water. Are y'all getting enough rain this year?

You can dig and divide them now if you wish. For best results, trim them down to about a foot tall so they can focus on rooting in again. In no time, the foliage will regrow and they'll soon wow you again.

Thank you for suggestions. I think I will untwine the crowded core, space them out, fertilize and water deeply.