I dont really think its too much nutes (only my opinion), dont know about that rhizotronic..all i can say is i used canna terra professional plus and added guano & rock flour to the soil (on photoperiod strain) because i found the canna soil best to use as a medium to put bio nutes in an cut my own mix (i guess ur soil is pretty much the same but u can check the stats at the canna website) and then i added some stinging nettle liquid manure every to every second watering with tap water (left standing for min.24h).
To make it u have to use fresh stinging nettle like 2/3rds of a bucket and then fill up with water (u can chop up the nettle to make it go little quicker) and leave it standing in a warm, best sunny spot for at least a week, mix it around and when it really getting stinky and u have bubbles the love portion it ready.
In my Opinion self made fertilizer is superior in cost (this liquid manure will cost u 0$) and brings up the really best,
may this helps to get your plant/s get as healthy as can be.
And by the way it makes the weed taste incredible good&strong
Mix the Liquid Manure like 1:10 with water for regular use if u think they need it stronger u can double or triple as well. But always check the reaction