What kind of deficiency is it?

I've been having problems with the brightening of the leaves.

At one point this type of things started appearing:




But this is where it has escalated.






They're turning 5 weeks old now.

I've been giving them 1/4 of the dose of nutes from the seed. First 2-3 weeks they were doing great, but then I transplanted them from rock wool into coco and I added calmag to the solution which turned out to be a mistake, because Canna Coco A&B which I'm using already has 5% of calcium and 2% of magnesium in it.. and coco has a tendency for calcium and magnesium deficiency only after 6 weeks of use. I shouldn't have added it.

So I stopped adding it.. and for few next days they got greener, but it didn't last. They started brightening again.

Now they're pretty fucked up.

If they turned that way almost overnight after adding calmag to the mix, did you flushed afterward? Too much calmag (you also need to consider the kind of water you're using) can cause a lock out

I just looked at Canna's light feeding schedule - http://www.cannagardening.com/growguide

.. and it turns out that I'm not giving them enough nutrients. At this point I should be feeding 2x the amount of which I've been feeding..........