read the guides on cocoforcannabis.com for the basics of soilless growing methods. You need to adjust your perception and fix numerous behaviours.
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Plant is clearly overfed. Nutes in your medium are far too highly concentrated. Give a few water-only with 10% runoff (maybe 20% for a bit). Let the plant start to pale back to normal before restarting fertigation.
5x a day is excessive. I think you get diminishing returns after 3x daily. You can google for information on this.
But, to do that, you need a plant and pot size that jive together. You are using way too much medium (pot is too big for plant) and i doubt you are watering to runoff with any of the irrigations, so, it stays wet and nutrients buildup everytime you water -- overfed, sickly plant.
The plant needs to be capable of drinking enough to warrant the multi-daily feedings. If not it's just stagnating, wasted water drowning roots.
So, do not choose the volume of water to give. You use as much as required to accomplish the task -- full saturation.. you want 10% runoff to ensure there is no buildup of nutes. The goal is a consistent level of nutrients at a ratio that does not impede each other. It should not rise and fall much in this growing method.
Like i said, the current size of plant and size of pot is not proper for multiple feedings per day, so stop trying to force a square peg through a round hole. coco isn't magic. Any medium constituted with the proper aeration and drainage qualities can be fed multiple times per day. coco is not the cause of that ability.
Until the plant is large enough and when the plant is healthy again -- 1) fertigate with well-balanced formula with 10% runoff, minimum. 2) wait for appropriate dryback and repeat. In coco when that top layers starts to dry, it's a good time to re-irrigate. feel the weight for familiarity, too.
if the plant can drink nearly 1/3rd of a saturated pot's weight multiple times per day, you can consider frequent daily fertigation.
if you want an idea of a decent formula, look in any 1 of my 3 new diaries for a per-nutrient PPM breakdown. This is not 'my' formula. It's a formula used by numberous fertilizer brands - jacks, cropsalt, megacrop, masterblend, southern ag, et al.... if it adds up to more than 4-5 cents per gallon mixed, it's overpriced.