Whats problem ?

Developing magnesium deficiency. Spots could be early stages of a calcium deficiency. Hydro is not very forgiving, but without much more info and/or a linked diary, it is almost impossible to be specific.

This an easy 1. Your PH is far too high U want to be around 5.7 this will give u a larger error for ph swings. Also wit coco its important to keep salts down.. that's them burn sitesbi reckon So feed water later tat day feed water or feed 1 day and water for 2 giving micros and other low EC nutes to follow up the heavy NPK feed. Regardless don't let it build up Hard flushes should be done weekly-10days max Take your ambient conditions of water going on. Flush with 1x the value of the pot. Catch as much as u can and you'll get your EC. this will whats currently left in ur pot. If its too high lower it to a more manageable level or if you haven't been doing this. A straight hard flush and starting doing what I just said But lower pH to more suit coco 6.4 is way off..

IMHO droplets of water. P.S.: I sent you a direct message some time ago, would you mind to answer please?

You provided no info on your grow. No pH numbers, no ppm numbers, no nutrients used, no environmental numbers..... might as well not of even posted picture's but asked the question.