Any advice??

Magnesium, but if its soil mix, most of cases why troubles starts is bad watering regime, aka overwatering, aka you dont have proper wet/dry cycle in pot. Lift your pots to know when to water them. Epsom salt and good wet/dry rhythm will sort those upcoming troubles, which will show up if you keep repeating current actions.

I think these answers nailed it. What you need to do to fix immediately without causing further damage is a light foliar spray of epsom salt. I’d run it through Ai to see the concentration given the nutrients you use. Don’t forget water on leaves and intense light don’t mix.

From what I can see: -The leaves show interveinal chlorosis (lighter green or yellowing between veins) while the veins remain darker. -The newer growth looks a bit twisted and lighter green, which can indicate a micronutrient issue rather than nitrogen. -The leaf edges and general color suggest the plant is otherwise healthy, so it’s not severe toxicity or overwatering. Given your setup (Plagron Batmix + Lightmix, BioBizz Ca, Greenhouse BioGrow nutrients), the most likely issue is: Magnesium deficiency Why: -Batmix and Lightmix both have nutrients, but the combination can cause high Ca and K levels, which can lock out Mg. -The pattern of lightening between veins on older leaves is classic for Mg deficiency. -BioBizz Ca (Calcium supplement) can make this worse if Mg isn’t supplemented. ✅ What to do: Add magnesium: Use a Cal-Mag supplement that includes magnesium, not just calcium, or Add Epsom salts (magnesium sulfate) at 0.5–1 g/L (about ¼–½ tsp per liter) in your next watering. Do this once, then again in 5–7 days if symptoms persist. Check pH: For soil, keep pH around 6.2–6.5. If your pH drifts higher, Mg absorption drops sharply. Avoid excess calcium: If you’re using BioBizz Ca often, reduce frequency — too much Ca locks out Mg and K. Monitor new growth: The damage won’t reverse on old leaves, but new leaves should come in evenly green within a week or two. Hope that helps! 😘

CalMag issue top - Mg lock bot - likely Ca lock do u know ur water ppm or u use CalMag bs other ppl using it ?

hey 👋 There is clearly an early stage of magnesium deficiency, which is causing discoloration between the leaf veins. But looking at your diary, I don't think the problem is due to your fertilization; the most likely cause is a problem with the pH of your water: aim for between 6.2 and 6.5. If the pH is correct, then it must be an excess of P, which blocks the Mg; in this case, reduce your Biogrow to 2ml/L, and not at every watering. You can fix that easily and quickly 👌