I don't know of anything other than normal, even poor, garden soil that's needed to make cannas bloom.

Are both groups in full sun? out of strong wind?
are they both the same kind?

If so, you might call your county agricultural extension agent & ask. Maybe something "different" is going on in your area.

Best luck!

Thanks for responding, sylviatexas - and yes, they are all from the same group of rhizomes. Now, I will say that there were crocus bulbs panted, at one time, under where the pale cannas are now, but that should not make a difference, other than crocus prefer a neutral soil.

Coincidentally, I planted some of these cannas near my foundation and they too, in years past, had very pale blooms, although this year the color is vibrant?? It's just a quandary to me.

I've got an extension service - maybe I'll see what they say. Happy gardening to you!