Mistery Auto #1 (caseeds) NORTHERN SPAIN

The plants are blooming like crazy. There are lots and lots of pistils popping out, but flowers still need to get a lot fatter. Everything seemed to be going perfectly, but right now there is a big struggle. And it is a pity, because now I don't have as much time as I had in the early weeks. The yellowing of the leaves is going upwards, and the ones that first yellowed are starting to die. You can see some necrosis in the pictures. Obviously is my fault, but I can´t tell at all what is happening. Earlier in the week I watered 2,5 l with the ash fertilized water. A possible reason for the yellowing could be a N deficiency, brought by the abuse of ashes because they degrades the N in the soil. Another possible reason could be a very basic soil, also brought by the ashes in that case. I also think my pH test is not working properly at all. On day 60, as the yellowing wasn't corrected with a PK ration, which I first thought of, I got worried and prepared a foliar spray made out of a potato and banana tea. So it had a balance of NPK with EC=1100. As it got even worse with the days, I kept investigating and realised it could be a Mg deficiency. So I watered with some Mg bath salts 'Epsom' up to the EC indicated with a lower pH of 6,3. As Mg is essential for the synthesis of clorofile, a deficiency of it could explain the lack of green in the leaves-they cannot do the photosynthesis then, and die-. Hope it works... And as always, any help would be great 👍