was the coco well-prepared? That can result in odd twisted and darker growth (k-tox), if not, followed by Ca and Mg deficiencies down the line or shortly after too. Even if the package says it is washed/soaked, doesn't mean they do a good job. e.g. i bought a 5kg brick of mother earth coco and nearly killed my plants. Took 37 days for a clone to grow. HAd dark twisted growth etc etc followed by Ca and Mg problems because the ion exchange sites leeched it out of what you fed and then it caused an overfeed of the supplanted K+ that released to be freely used at that point.
Good news if this is the case... give it time.. it will work through it. I'd suggest over-irrigating with extra run-off of your normal nutes... This will quicken the cation exchange going on until it hits an equillibrium, at which point it functions as an excellent substrate (i love coco once i learned how to prepare it correctly)
--- other options:
Make sure any water-only dose is pH'd and know the pH of your fertilized irrigation to ensure it's near a safe range. Some fluctuation is fine and even beneficial, but you don't want wild swings in pH.
It's difficult to know for certain what you should do, but the best route to take is to take the pedal off fertilization for a few days and see how it reacts. If it is a deficiency, it will be obvious very quickly and simply react with virtually no negative impacts in a very specific and certain way.
If it is a toxicity, you just avoided making a problem 10x worse by dumping something unneccessary into your coco or soilless medium. Also, nothing you can do with a tox but wait and irrigate.
Take the route of the most likely, but also consider what's less obtrusive to start, if multiple choices. pH is obvious and can quickly react to a measurement. Leaf symptomes have all sorts of false positives that will throw you off.