You've got to have pretty eagle eyes to see that... you're worrying over nothing here! I would, though, be cutting back on the Canna A a bit as it's got a lot of nitrogen in it and since you're heading into flower, this might lead to some problems... the yellowing tips are just an indication that you're feeding them a little too heavily so knocking back on that would help there as well. But going forward, I don't think I've ever seen tips NOT turn a bit yellow and, unless they start to turn brown and the brown gets a lot bigger, you really have nothing to worry about!
Cheers! And good luck!