Thanks man,
That V shape of yellow on the fan leaves, in my experience is usually indicative of a magnesium, or potassium issue.
But both being mobile, i'd expect to see the symptoms towards the bottom of the plant, and progress upwards when deficient. I'd also expect general leaf fade, and interveinal chlorosis. But we're not seeing this.
My thoughts...
It's quite a high pk value on the buddha. I realize it's only 0.25mL / litre, but i would try cutting that dose down to 0.15 or so.
Maybe lower the calmag slightly too. 20% volume to your Canna ab seems slightly excessive to me.
I'd also try feeding an extra time per day, and see how it goes.
That's what i would do.
I think it's just a little overfed, and the npk ratio might need a little tweaking too.
Good luck.
Edit: if it keeps it up over the next day or two, come back here.
Also if it does keep progressing, before you report back, check the ph of the waste.
It's pretty normal for coco to have waste readings above ph6. That is fine, and normal.
What would concern me, is if the waste ph reading was particularly low. It happens sometimes.
Don't worry about this for now. But if the problem persists, check the waste, and include it when you report.