It does look like a Cal-Mag issue at first glance, especially with those rust spots and the yellowing between the veins. But in week 9, this can also be part of the natural fade as the plant is finishing.
I’d say it’s likely a mix: a slight Cal-Mag deficiency, combined with normal late flower senescence. At this stage, the plant is pulling nutrients from the leaves into the buds, so some yellowing and spotting is expected.
If your pH has been stable and you’ve been feeding properly, I wouldn’t overcorrect now. Maybe just a light Cal-Mag support if anything, but don’t push too hard this late.
Also, you might want to raise your light a bit. Sometimes reducing light intensity slightly can help take stress off the plant, especially in late flower.
Overall your buds look good. I wish you some nice Couch events. 😊