Leaf vein browning

A Calcium deficiency is the most likely culprit. It is not a magnesium or potassium deficiency.

I cannot make a definitive diagnosis based on this photo alone, but there are a few clear indications. What I can see: The leaves are predominantly dark green. There is a bronze/rust-coloured discolouration between the veins, whilst the veins themselves remain relatively green. Flowering seems to be well underway. The most likely causes are: Magnesium deficiency (most likely) This often starts on older leaves. You’ll then see discolouration between the veins, which may later turn bronze or rust-coloured. This occurs regularly during flowering, especially if the plant is taking up a lot of potassium and calcium. pH problem Even if there is sufficient magnesium in the soil, an incorrect pH can prevent the plant from absorbing it properly. This often occurs when the plant is over-fertilised. Early-stage potassium deficiency (slightly less likely) In this case, you often first see yellow or brown leaf tips and leaf margins. I can’t see this very clearly in this photo.

Sounds like a big dose, what is your runoff EC? I'm sure you will find the culprit there. If not perhaps your root zone is just unhappy and needs a good flush to eliminate any "channeling" in the media.

1tbsp per gallon as top dressing. 3-4tbsp per gallon on a fresh mix. Intervienal but not marginal.....high soil ph or poor soil drainage/compaction/composition. High levels of organic matter and/or with a drifting high soil pH will bind available soil manganese into insoluble complexes. Causes tissue between the green veins to die Manganese is the central engine of the Oxygen-Evolving Complex (OEC) in Photosystem II. Without manganese the light energy fails to leave the veins and overloads and "frys" the cables so to speak (veins).

Good afternoon, From an analysis of your diary, I think we're facing a pattern quite localized in the veins, which makes me think that there is something beyond normal aging, maybe a deficiency, perhaps potassium, or nutrient blockage due to pH changes... But I don't know if it will be worth trying to solve this problem since the harvest should be coming soon.... Let's see what other opinions come up...