Maybe someone familiar with the Canna line will jump in. My very limited understanding is the A+B is supposed to be complete, and designed for coco. So I'm not sure what the Rhizo / Cannazyme might be doing for you at this point. My uneducated guess is that it's not needed.

Calmag is generally recommended if you're using distilled water, esp. in coco. But again, A+B may cover that requirement for you. You might wanna research that, sorry, IDK. Seems like a lotta stuff for younguns, especially sativa-types which can be very light feeders.

I normally alternate feed / water in coco. If feeding every time, I do a little more runoff (~25%) and tune the nutes a little lighter to prevent buildup in the medium. I would definitely check the ppm of your runoff, and compare it to what's going in. Might be too hot. How were the plants doing at half-strength nutes?

I have seen lots of folks have problems trying to veg under HPS. OTOH, lotsa peeps here get good results with it, but 24/7 @ 600W seems like a lotta power for seedlings. I'd be doing this under a couple 6500K shoplights and save some $, if nothing else. I really like bluer lights for veg. YMMV.

I'm gonna suggest your pH may be a problem. If you're putting in nute solution at 5.8-6.0 and it's coming out at 5.0, the pH of your coco medium's gotta be lower than 5.0 to knock it down that far. If your pH in the pot is <5.0, you're risking "lockout," which simply means your plants can't use whatever nutes may be there (nitrogen included).

A thorough flush (3X pot volume) followed immediately with a light feeding should help. At least, in coco, it's not gonna hurt... pH below 5.2 in coco has been ugly for me...
DreadedHermie Reviewed by DreadedHermie on . 1st Grow: Please Help with Canna Coco + Plants turning Yellow Hello All, First off, thanks to all the people that actively post! It is because of their knowledge, I have been able to make it this far :) Now on to business... It has been about 3 weeks old since the seeds popped through the Coco. I have noticed over the past week or so that the leaves are starting to turn yellow. They are still growing but I can tell something is wrong. I am guessing it is a Nitrogen deficiency, but I am so new at this, I wanted to ask the pros! Rating: 5