Been having this problem for about a month now Here’s what I have going dwc 1.Kept my ph between 5.2 and 6.2 2.using Sensi grow nutes a&b with b52 And cal mag 3. Using tap water with a ppm of 120 and I let the water sit for 24hrs 4. Ppm has been lowest 400 and the highest 1000 depending if I flush or not 5. Ec around 1.7 6.Grow light hlg 300l r spec 24 inches from plants 7.i have a ventilation system going 8.Temperature between 82-85 9. Humidity between 40-50 Whatever This is it started on my older leaves and now It’s catching up with my new ones i can’t figure it out to save my life the roots are white/healthy and growing long Not weed rust it doesn’t rub off on my fingers it starts out at the tip of the older leaves in patches Then they get dry/Crispy and curl up
Keep an eye on the new growth. The new growth is what tells you the plant is healthy and growing. I would just keep an eye on the bottom leafs for now. Wouldn't hurt to swap resivour out with fresh one to reduce residual salts lowering the EC some.
well the bottom leaves got so dried up I just snipped them off those are the ones in the pictures but the spots are starting to spread to the new ones it’s like it’s eating up my plant slowly everyday it gets worse