You seem to have a handle on things. The 'second' compost is not required and is just mainly a source of good bugs and more diversity. If I had a worm bin going the additional compost wouldn't be used.
The Oly Mountain compost is what I'm using in this run. This is WELL finished compost and VERY dense. It stains your hands!
I used Dynomoco in my last run. Root systems are crazy in EBs, but I do think it made a very good difference.
What you have to work with, it should grow great canna. Just remember, it takes time to be made available to the plant. That's why I do a limited flower amendment at the time of set up. I do the second and hopefully the last top dressing the first week of flower in autos.
As a backup for flower, in case of a heavy feeder, I'd get BuildABloom. It's quickly available and helps with uptake of other nutes with the quality aminos.
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I added it to the roster in the last run. With what you have and that one addition of BuildABloom, I think you'd be fully covered for anything that may come up nute wise.