Yellow patches on old leaves

Hi, Before you think about more nutrients, maybe check the light, temperature, airflow and your watering technique ;) Biobizz All Mix should have enough nutrients on its own. I recommend experimenting with a 5L pump spray bottle and a pouring cup.

Your using organic nitrogen if your into the allmix and biobizz. Organic nitrogen is not readily available and is attached to the rate of nitrification to determine how fast it is converted. Nitrification is linked to pH. Basically it won't convert nothing (very little) at a pH of 6. Lower it goes, slower it goes. A normal flush will wash all your nitrates but leave all the nh4+. Trapped. Takes (4-5x flush water) to get rid of nh4+(ammoniacal) Having more than 20% ammoniacal nitrogen in a medium is detrimental because it can lead to plant toxicity, as plants may accumulate ammonium in their cells, causing damage. High ammonium levels can also lower the pH of the growing medium, especially when plants are exposed to cold temperatures, which hinders the nitrification process and can result in ammonia toxicity. Additionally, excessive nitrogen, particularly ammoniacal forms, can cause overly lush growth, delaying maturity and making crops more susceptible to diseases, pests, and environmental stresses. Ratio of charged cations in the form of nh4+ are likely skewing the pH to acidicity causing problems all around as soon as you get to 5's aluminum starts to break its bonds. Be careful not to go lower. Ph balance is off due to large portions of unfinished nitrifying nitrogen, skewing the ratio. If there is CEC capacity to do so you can balance the pH by adding oppositely charged nutrients once the pH balances closer to 7 the rate of nitrifiction will instantly x5x6 around a pH of 7. Or flush it allllllll and start using nitrates.

agree about Mg, try to add around 35ppm per L also she seems to a bit light on the N Biobizz All mix soil has no Mg ? Realy ? wtf xDD EC = 2.2 that could be the issue K and Mg are antagonists so that's why Mg could be locked or there just no Mg at all So Biobizz with EC = 2.2 + ur last feed doesn't look right

Magnesium i would say. So double check your watering habbits, is wet dry cycle happening and check ph. Never value colour of leaf under light, either day light , aka sun or night and mobile with flash. Think she is closer to healthy green, than sick yellow under daylight ...