No need to charge the coco. I use half the recommended dosage from the Canna chart at 5.8 PH and have had good results after my initial disaster using Canna with incorrect concentration (overdose).
Others will recommend the full concentration. I made the mistake of going full concentration on my first Canna grow and had N overdose problems. A lot of it is strain dependent. Some strains will tolerate a lot of abuse, others will not. Canna wants you to blow money on their products so it's not a far stretch to assume their feeding schedules are based around this goal. Use half dosage, and if you see deficiencies, your strain may be a heavy feeder, then bump it up a bit.