My plant looked similar but much worse, and i'm 99% sure it's K deficiency, maybe a little but of N also, but it looks like mainly K.
I had magnesium deficiency and didn't have Epsom at hand, so i used Calmag which has much more Cal than Mag. My hard tap water also has lots of Cal so i overdosed my plant with calcium, which locked out magnesium and potassium.
You're adding Calmag every other watering but do you use tap water or RO? Because that could be your issue.. With tap water you don't really need Calmag besides few exceptions. Many nutrients and supplements already have some calmag, and combined with tap water it's the perfect amount.
I don't know if flushing would help, but i did a flush anyway and just used few teaspoons of Epsom salt and lots of Bloom nutes after. It helped and the yellowing slowed down, somehow i made it through harvest with yellow leaves lol..
And don't worry, you can still make it through harvest. Here's some pictures of my 1st grow, no judging please haha.. But as you can see the yellowing started very early but it managed like that for around 1 month until the end. It was an early harvest but ok weed for a 1st time, around 30g and better than street weed in my area
You are much closer to harvest than i was, and you have much less yellow leaves.