Can’t fix this problem

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
 

Attachments

Top