Leaf deficiency. Not sure which one?

First ever post.

Need some opinions on a leaf issue I have. Can't figure it out. Any ideas would be much appreciated.

This leaf is about half way up the plant. Newest leaves have small signs of rusting. Can upload more pictures if required.

Thanks in advance!


Day 25 of Flower
Afgan Kush
In Canna Seed Mix soil with 20% perlite.

250w HPS

Day temp : 25c
Night temp : 19c
Humidity : 42%

pH : 6.5
EC : 0.6

Canna Flores
Canna CalMag

Looks to me like some serious pH fluctuations.

Feed rate on your cal/mag? Looks like she wants more.

Not considered pH fluctuation. Good point. My run off was on the low side was around 6 and wanted to raise it a bit. So have been watering with ph 7 to bump it up. So could well not have liked the sudden increase around the roots.

I'm dosing my CalMag at 0.4EC. Watering with plenty of run off every 3 days.

I watered once without CalMag to get my soil nice and clean. But could well have not like too.

My 2 Afgans seem to displaying the same issues.

I have 1 Top Dawg from Barneys which doesn't have any issues. Is perfect.

Thanks for the responses