It's more a case of it being pointless really. If two bottles worked any better than one, I'd say go for it. They don't. So I say don't.
Canna is in two bottles A&B you mix.
If all of them work great than there is this:
Amazon:
2-gal of GH micro and Bloom- $56.46
2-5l bottles of Canna A&B--- $91.99
2-gal of Floranova---------- $125.72
no brainer