Runoff really matter ?

Hey Growmie, sounds like you’ve been doing your best to tackle a tough situation. A runoff pH of 4.8 is concerning; that level of acidity can severely limit the availability of essential nutrients like calcium, magnesium, and iron, which are crucial for healthy new growth. The yellowing you’re seeing at the top is likely a sign that the plant is screaming for help due to those deficiencies. You did the right thing by flushing with RO water and then following up with a light nutrient mix using Cal-Mag and Tiger Bloom. Seeing the pH only rise to around 5.2 after 30 liters suggests that your medium had a heavy salt buildup or poor buffering capacity, making it tough to swing the pH back into the ideal zone. At this point, it’s smart to let the plant settle and allow the root zone to dry out slightly before your next move. For your next feed, make sure your nutrient mix is well-balanced and pH’d to around 6.5 to help nudge that root zone back into the optimal range of 5.8–6.3. If runoff still stays low, another gentle flush with properly pH’d water and light nutrients may be needed. You might also want to consider adding something like dolomite lime or a root zone conditioner to help buffer pH long-term. Keep a close eye on that new growth over the next day or two. If the yellowing doesn’t spread and the plant keeps growing, you’re likely back on track. Let me know how she looks soon. Growmie, you’re doing solid work under pressure.