Any advice ?

It looks like there is something extra in the coconut and there are surpluses and then shortages. Otherwise, I don't know. Ph and ec everything is normal. I've been growing for a long time, but I don't understand this.

I don't have Diar, these are my experimental plants. But it starts to happen whenever I water with calmag only. I water twice a week most of the time, once normally, + cal mag and other fertilizers and the second time I just balance the ec to 0.4 without fertilizers. It always shows up within two days.

Not real sure here but it could be the beginning of a potassium deficiency.... do you have a diary for this grow? None of your diaries look like this particular grow which is why I'm asking.... you can always link a question to a specific diary by asking your question at the bottom of your diary page... But back to this.... Check your pH... if you're growing in soil, it should be between 6.0 and 6.5 - if you're growing in coco or hydro, pH should be between 5.5 and 6.0... If that's ok, you might consider giving a small dose of PK boost... Without a diary, I really can't figure anything else out... Good luck!