Hey Growmies, I have an issue with one of the girl...

Great videos, Yan, love the approach, very detailed. Magnesium, being mobile, if it were a true deficiency, it would show its mobility on old growth doesn't mean its not locked out. Last 3 weeks, I noted you added calcium, mag, along with calcium nitrate and magnesium sulphate, so even though they are in small amounts, the ratio of cal to mag is important is generally kept 4:1 to 7:1 for optimal growth. Antagonistic effects between calcium (Ca) and magnesium (Mg) in plants typically begin to appear when their ratio in the soil or nutrient solution is imbalanced, especially when the(Ca:Mg) ratio in the soil exceeds approximately 4:1 to 8:1, or when there is an extremely low ratio (high Mg relative to Ca). If your pH is still in range, then it's a hazardous guess at an antagonist skew of ratios effectively "locking out" and causing the appearance of deficiency. Also looks like the edges of some leaves are starting to show K, which would also be affected by the antagonism if it were high enough. Stems look far more purple on the yellower plants, indicating P or possible oxygenation issues (pot furthest from fresh air/intakes). Can't lose your calcium or phosphorus, vital for micros and sugar conversion. As soon as oxygen goes low, iron goes, nitrogen goes, all cellular respiration stops, no energy, no nothing Sorry, I can't be more specific, being in Coco it's harder to deduce, I think it's an antagonistic skew affecting cation exchange, exacerbated by environmental factors like lack of oxy in rootzones, possibly different things creeping in. Wouldn't expect oxy issue in coco, but those redish stems are more commonly P. Good luck, I'm not sure.