Hi Loz
You're having some troubles with the coco I see.
I've done a good bit of reading on through the canna info pages on the canna usa website (canna coco user myself)
You know you've burnt them - but on my screen i'm not seeing the pale underfed look - just a bit nute burnt. That'll definately slow them down.
Are you using canna coco A&B as your base nutes?
Have you checked the NPK ratios on the CalMag - Mine contains quite a hefty N dose in it.
Are you checking the EC (PPM) before watering?
My water has a backround EC of 0.5. Canna recommend never feeding under 0.8 E as it effects the buffers.
My first waterings I will add Rhizotonic at 4ml per litre (no EC and great for roots) - I will add 0.75ml of both CocoA&B base nutes
If you are using COCOA&B - makes sure you stir the A in properly before adding the B.
This little mix should take my ec around 1.0 - 1.1 - Then i will add water to dilute to 0.9 or 1.0. Then i add my PH down to 5.7 - 5.8
This shouldn't burn the little ones - and hasn't burnt my 5 day old seedlings.
Check out the coco forums - I've summarised a lot of good info from the canna FAQs that are hidden away on their site. Its in a sticky at the top and is relevent to Canna Coco.
Hope this helps!
Blue ^_^