Brown spots, yellow leaves last 2 weeks of flowering!

[Ladyblue]

Help! What's happening to my girls? (Northern lights strain) With only a week or two left of flowering stage to go, and suddenly, I've got over 50% of the leaves turning yellow with brown spots! This happened fast!! I haven't done anything different, and I see no bugs. This is only my second grow, but last year was a complete success! (Well, except for the fungus gnat battle - but, I WON!😊)
Any help would be mucho appreciated!

[9fingerleafs]

hey there welcome (: looks like a severe deficiency, could be due to lack of nutrients or a problem in the roots like ph. what kinda soil are you using? do you feed anything? do you measure ph? probably this close to harvest it would be better just to remove crispy leaves before the crispiness gets inside the bud and harvest.