Seymour, you manage to pull me in two directions on this one ! I wonder whether a compromise of 1.7 is the right thing here. I thought an EC of 1.6 sounded high enough to be honest, but Think Different seems to be drinking those nutrients at an unfeasible rate for the age of the plant. Being somewhat risk-averse I wouldn't want to push her too far. Although right now the best judge is you, and I think you already know you want to push this new strain to the max. Just be gentle with her man. Go slowly with her and remember it is Ok to keep it at 1.6 for a day or two if you sense you need to.
I have been in touch with the experts at Canna nutrients in Holland, those boys know their stuff. Man I would love to know their thoughts on this and the previous comments on possible Ca/Mg deficiency. Lets see what they say, I will let you know. They are following this too.