Interesting... so maybe you don't want to adjust your nutes yet. I say that because if you were too high and locking things out then your mixture may have been just fine. I'm not a big believer in changing a lot of things at once so maybe it's wise to see how they respond with the new pH range before tinkering with the feed.It does say on the Canna website and after being sent some thread links and doing some searching on here a few people have had similar issues to me and when they bring the pH down everything sorts itself out.
At least I now have the info I need to sort this grow out, I just hope it's not too late.