I am growing in soil, suing Pureblend Bloom original, diluted to 3 tbsp/Gallon, and just started adding 1/4 tsp of carbo load. One gallon of the 'mix' lasts about one week for three plants that are almost 3 ft high.
The fertilizer really dropped the pH level, so I started adding a tiny bit of pH Up to bring the pH to around 6.5
Hiya Vancouver guy
I'm not convinced in my mind that it's Mg deficiency affecting your plants.
It's never easy to differentiate between MG and N def's in the early stages because they both look quite similar to each other. Canna uses plenty of Mg as well as the other three main NPK nutrients.
In your grow journal you posted on the 26th June that you transplanted into 2 gallon pots, but you posted a picture of the plant as at the end of May. When did you transplant into those 2 gallon containers and what soil did you use? This is critical information to understanding your problem. If those plants have been in those containers since the end of May then it's highly likely it's Nitrogen.
I'm not sure who's been advising you on nutrients, but what you appear to be using isn't feeding your plants correctly.
Botanicare Pure Blend Original, which is 0.5-0.5-1.0 for organic, bloom fertilizer.
See those figures 0.5-0.5-1.0? 0.5 ppm of Nitrogen? Botinicare appears to be a bloom stimulator, not a nutrient bloom fertiliser. You need to get a Grow fertiliser and a Bloom fertiliser with NPK ratios along the lines of 6-3-4 for Grow and 4-6-6 or something for bloom.
Carbo load is merely putting carbohydrates into your soil that feed the micro-herd, when there probably isn't any micro-herd because you didn't add any and used a sterlie potting soil. So Carboload is probably doing absolutely nothing to your plant, whilst it's starved of NPK nutrients.
The liklihood is therefore, that your plant is Nitrogen deficient, not Mg deficient, although is still impossible to tell from simply looking at the plant. My advise therefore is to get the correct Grow and Bloom fertilisers and use them at 1/4 strength to start with. If the yellowing stops and doesn't spread then that's the answer. If it continues then it's likely to be Mg.
Note, yellowing leaves do not suddenly revert back to being green again. What you need to watch for is a slowing and halt to the yellowing of leaves not a reversal of the existing yellow ones.
Good luck with your plant and your grow.