Tropicana was a bust for me also. When I grew what I called Canna W (so I would not have to pronounce that full name,
) I lived on an island with heavy soil that was essentially sand and old marsh muck. It held moisture well, sometimes too well. Perhaps that is why the conditions were perfect for germinating the canna seeds. Also, I was not so neat and rarely snipped off the seed pods unless I needed them for a propagation class. I probably gave out many hundreds of seeds over the years. The species cannas always did better for me there. Right after we moved here I rescued a Salmon Canna Canova (?) from Lowes, it is a miniature, less than 2', and has shown no signs of disease or insect problems here.