hey hey Looks to me like you have yourself a case of nute burn.... This can be caused by a few things but mostly by too higher ec or ppm. Alot of new growers get nute burn due to not knowing the signs of PH lockout, so they see there plant lacking nutes so they up the PPM and then whadda ya know, burnies on ya leafies Now i would still be looking at a PH lock out or even a salt build up in your substraight so the best way to figure out the issue is to find out what PPM you feed them at to start, then next step i would flush with 10lt of PH adjusted water before you do this test the PPM of your tap water you will need this later to compare over flow PPM. Catch some of the overflow and we need to test that to cancel out 2 2 problems, first of all check the PPM of the waste water, is it the same as the origonal PPM you started with??? If so i would be guessing you have a salt build up in you coco this can be fixed very similar to a PH lockout but lets test that first. The same test sample now needs to be tested for any PH increases. So if you test your PH and it has changed majorly from what you origonally had then im guessing you have PH issues as well. Now to fix both problems is quiet simple, for Salt buildups simply flush with straight water PH adjusted (if you think your plants are susceptable to PH issues, i never used to worry as my plants didnt care much) and keep flushing and testing the run off untill you get to a similar PPM that you started with..... To fix a PH lockout same thing really but make sure your PH is adjusted before you flush and test the PH after each flush, a little tip i used to use to do it quicker is use fairly low PH water at the start if high PH is your issue and vice vera if low PH is the issue, usually its high, and for the last flush once your close to getting it right make sure its spot on the PH that you want. Another tip for you would be to switch to a coco specific nute such as canna coco, as i know its hard to get coco grows spot on with normal nutes. And make sure you aint leaving any run off sitting in those bowls at the bottom as that will be part of the issues if you are.... hope that helps and happy growing!!!