I believe that is not the nutrients, the problem started when the EC was 0.30 (very low).
I'm following this table from General Hydroponics, link below:
http://generalhydroponics.com/site/g...REC-Charts.pdf
I did a test with a rockwool cube placed in pure distilled water and pH adjusted to 4.0 and the next day the pH rises to 6.2.
Lower the pH to 4.0 and again the next day up to 5.8. I'm doing this procedure until it stabilizes. I am almost convinced that the problem is the large amount of moisture that accumulates rockwool, and watered three times a day. I removed the excess water and I am watering with spray directly on the leaves. I read that excess water blocks the absorption of some nutrients, so I added a bit of Mg in the solution to meet the needs that I believe what was happening. I see a positive result, did not notice new spots. In the next week I'll reconnect irrigation to once a day and very little dripping.
Tomorrow more news writing.